Around 20 years ago.

Always keep boarding passes as evidence in case miles don't get posted.

Passport control signage at BKK.

https://cimg0.ibsrv.net/gimg/www.fly...986d21c580.jpg

I had a few experiences over the years:

2008: Landing in LHR from Brazil with some relatives. My aunt (brazilian passport with UK residence visa, married to a a UK citizen), her daughter (UK child passport holder, no Brazilian passport yet). No entry issues with my Brazilian passport/student visa at the time. My aunt was travelling on a new passport but she left her expired one at home (that contained her residence visa). On her daughter's UK passport, the surname was her father's surname (he was not travelling with us). However, as my aunt did not register her marriage in Brazil, her Brazilian passport still had her maiden name.
At LHR immigration, the border agents were extremely suspicious because my aunt's passport did not have any visas, and the surname on her daughter's passport did not match. We spent nearly an hour back and forth with the immigration officers. They were nearly close to deny her entry into the UK and send her back to Brazil. In the end, she was given a 3 day visa to sort out her passport situation (she eventually got her residence visa transferred to her new passport). To add insult to this, our luggage did not arrive with our flight and we had to spend another hour dealing with lost luggage forms.

2012: By then I had permanent residence in the UK, so my Brazilian passport had a sticker showing this residence right. Shortly after I got my permanent residence, the UK government started issuing ID card visas for foreigners instead of attaching the visa sticker to the passport. For some time, border agents in some countries (mainly Poland) were often questioning the legality of that visa sticker as they were expecting me to produce the UK ID card visa. Many times, the passport was taken to another room to be checked by senior border officials.
After a couple of those incidents I decided to apply for UK citizenship to stop all this hassle. And then came Brexit....

Entering Tel Aviv, Galápagos

A couple of examples come to mind:

Crossing back to West Berlin from East Berlin in 1981 at the Friederichstrasse U-bahn station - The DDR border guard reviewed each detail on the passport, glancing back and forth between me and the document to compare, then looked at every visa page. I was ultimately let through without a word, but it was a tense situation as other guards with machine guns and German shepherds kept watch.

Several years ago I had a long layover at LHR so I flew to DUB to have dinner with my son. Spent the night and flew back to LHR the next morning for my flight back to the US. About a year later at the passport check in DUB the officer reviewed my passport and quizzed me in detail and with considerable skepticism about why I would visit Ireland for just one night.

Ah, yes, that reminds me of SFO/YVR for lunch. It was basically a full day segment run on AS many years ago - just over $100 per person. YVR agent didn't believe me. We had basically a laptop bag as our only "luggage" and she started grilling us and then she finally asked how much the ticket cost - I said about $100, pulled out the ticket receipt, and we were on our way. And that is why on international travel, I typically have a printed receipt which also contains the ticket numbers (which are lifelines when there are technology burps).

Canada. I’m a US citizen with a US passport. I was booked BOS-YUL-YVR-SYD. It was a great business class fare on Air Canada right after Australia opened back up from the 2020-thing.

When I arrived at YUL, the border guard asked me for the purpose of my visit to Canada. I told him that I was transiting on a domestic Canadian flight to another country. The guard scoffed at me and said “What do you mean you’re transiting?” as he didn’t believe me (or he could have just been French Canadian) and after showing him my three boarding passes from Air Canada, I was let in after additional scoffing. (Hey, YOUR national namesake airline sold me this itinerary!)

(I ended up staying overnight at YUL because it was Air Canada’s summer of delays causing me to misconnect there anyway)

On the return, I was booked on SYD-YVR-YYZ-BOS and the border guards at YVR couldn’t have cared any less when I entered.

Edmonton in December
 

I flew to Edmonton in late December a number of years ago to visit a friend who had moved back there after living in US for 25 years. The questioning went something like this:
What is the purpose of your visit? To visit a friend,
How long have you known this person? 10 years.
How do you know this person? From Tae Kwon Do class in New York. She moved back to Edmonton to be with her elderly parents.
How long are you staying? 5 days.
Have a nice visit.
I think he was wondering why someone in their right mind would visit Edmonton in late December, and wanted to make sure I was legit. This was a first for me. Usually it's where are you staying, and how long will you be here?

I know a number of people who would fly to Edmonton in December for the right hockey match.

A pretty standard experience in many countries I would say. The questions they ask are only partly to elicit the information they ask for, it's also a means of engaging you in conversation and, for want of a better expression, seeing if you come across as shifty.

Heathrow agent: It says here you went to Amsterdam.
Me: Yes.
Agent: I don't know why anyone would go there. Quite a dirty place, isn't it?

Not really scrutinized, but poor form by the agent to badmouth another place.

Funny: A six hour layover at LHR in the spring On approach I noticed a pretty park in flower in Hounslow. I took the tube a few stops and spent a few hours wandering around and sitting on benches in the sun. On return passport exit control was very suspicious, "what did you do in 3 hours landside?" When I said I went to a park in Hounslow the agent laughed and waved me on, saying he lived in Hounseow and was glad I enjoyed their park.

Not funny: Exiting Bangui, Central African Republic, where you ride a dugout canoe across the Ubangi river into Congo. Apparently when I entered (overland from Cameroon) someone failed to stamp my passport correctly, and I could not get an exit stamp without an entry stamp. They seized the passport, so I immediately went to the embassy, which sorted it out without too much delay.

The DDR (East Germany before reunification). I was living in West Germany with a student/residence visa and wanted to spend NYE weekend in Berlin and traveled by train. At the first train station after the border (entering the DDR), the train stopped and a lot of people that I assumed were Russian soldiers entered the carriages while more of them patrolled outside with vicious looking German Shepard dogs on tight leashes. When several of them entered my compartment, they turned on the overhead lights (it was daytime and fairly sunny so lights weren't necessary), looked below the seats and above in the overhead luggage storage racks. Then they demanded passports in turn and looked at all of the pages carefully, scrutinizing the photo versus the person at least three times. When the process was finished--it seemed to take a long time, although the train arrived on schedule--all the soldiers left and the train moved on. [The journey from Berlin back to West Germany was similar, although it was more understandable in that they didn't want DDR citizens to leave without permission.]

A few days later, I decided to visit East Berlin for a day, entering through Checkpoint Charlie, which I believe was the only option for USA citizens on foot at the time. To enter, you leave West Berlin (IIRC simple stamping of passport) and then spend about an hour in "no man's land" while East Berlin officials take your passport out of your sight. While waiting, you must change about $10-15 of West German marks to East German marks at the official 1:1 exchange rate. I also had to list the exact amount of every bit of money I had with me, which included random coins and small bills from at least a half dozen European countries plus some USA dollars and traveler's checks. (Does anyone remember those things?). During the day, you were required to write down every pfenning spend and the purpose (including 5 cent fees to use restaurant restrooms!) and upon return to East Berlin, dispose of all remaining East German marks (no souvenirs allowed) and show that you have the correct amounts of foreign currency with with you. The exchange rate was horrid and the government was strictly enforcing the prohibition on black market currency exchanges. However, you could eat reasonably well in East Berlin for very little money, so that was the recommended way to spend the required amount.

Again, these aren't random conversations - they're trying to see how you react, and judge whether that throws up any suspicions.

I had a strange experience at Pudong airport shortly after it opened. My girlfriend and I were changing planes en route from Bangkok to Ohare. The first leg was on Thai Airlines and the second was on United. We got off the plane and thought our 2-hour layover would be a cakewalk because the first plane was on time. We left the jet bridge and saw a lady holding a sign for passengers connecting to the United flight to Chicago. Even better, I thought. Then she opened a door that said restricted and led us down this hallway. I wondered what President Bush had done to aggravate China. There were windows on one side of the hallway overlooking the immigration area. There was a mass of people waiting to get into China.

We took a few turns, went down an elevator, and suddenly found ourselves at the head of the line. We were US citizens without visas or documentation permitting us to enter China. GF asked me what was going on. I was not sure. I was beginning to worry if we were going to jail. The woman leading us only knew enough English to tell us to follow her and that everything was okay. The immigration agent for China looked at our passports and the forms we had been asked to fill out. My form was damp with sweat and thus illegible. The immigration agent wanted me to fill out another form. The lady assisting us told her no. The immigration agent won that battle, and I was asked to complete another form. I did. The immigration agent refused the second form. The lady assisting us started screaming at the other agent to let us through. They yelled at each other for a few minutes, and then we were permitted to go through.

The lady explained that we had to get our luggage and recheck it. The luggage belts were not working, and we had to find our luggage in this room behind the baggage claim belts. That door also said restricted. We found our luggage and took it to the United counter to recheck it. Our flight was leaving in about 40 minutes, so we had to jog to the gate to board our plane to Chicago. We made it, but we were both stressed and sweating.

I believe what happened was that Pudong was still under construction, and the part of the airport where checked luggage is switched from one flight to another was incomplete.