I know that this is a very simple question for some of you more experienced travelers.

I note that I can book different airlines on outbound and return flights? Does this cause any sorts of complications? I've always traveled on same carrier, for all parts of trip. On upcoming trip to RDU to Montana, I get some better options on Expedia and would like to try them.

Expedia tells me that seat selection is available on "some flights". What exactly does that mean?

Thanks so much.

As long as you have ONE ticket with all of the different airlines you want which has been ticketed say by Expedia, there would be no complications. Some airlines let you book seats online and some don't.
I remember last year a situation that made it complicated. I had two separate tiks SJC-LAX on UA and LAX-BOM on AI - that entire itinerary wasn't connected up in UA's system.that made it complicated and I spent about 45 mins breaking my head to finally have my bags checked all the way..
Hope that helps..

Since the question isn't about miles and points I'm going to move this thread to TravelBuzz.

Regards,
Gary
aka gleff
MilesBuzz and Delta moderator

Given the situation you describe, you should have no complications.

Now, if you had different airlines *within* the outbound or inbound flights, that could be a very different story. (Protection for late or cancelled flights, checkin procedures, having a long trek in and out of security for your gates, etc.)

But as long as you're with the same airline going out, and the same(but different) airline coming back, I don't see any problem except maybe making sure all of your miles post correctly.

It's not going to cause much complications except for the fact that your airfare will skyrocket compared to flying the same carrier rt.

I do this fairly frequently and it has never been a problem ( but yes it can be expensive). The only time anyone has mentioned it was flying BA from Gatwick to Belgrade. The checkin agent said that she needed to see a return ticket as the visa I had required proof of on onward travel out of Serbia. I showed her my Swiss ticket which in fact was from Tirana as I was flying from Belgrade to Podgracia and then driving down to Tirana and she was fine with that.

That's not always true. I've gotten some weird combinations out of Expedia. I had to find my girlfriend a flight to PHL in May. The cheapest flight I could find was AA ORD->PHL with a US/UA return leg (US: PHL-RIC UAexpress: RIC->ORD).

More and more I use different carriers and even different airports for trips. My latest was US: DCA-FLL and DH: PBI-IAD. Before was B6: IAD-LGB and AS: LAX-DCA. As long as the carriers offer reasonable one-way fares, I can mix and match carriers to save money, time, or stress. Note that in these examples, the legacy carriers offer reasonable OW fares (1/2 the RT rate) to compete with the startups (Independence and jetBlue).

I have encountered no complications.

I do this too in Europe. The only problems I have when I have one return ticket is sometimes the frequent flyer program, seat choice or self checkin does not work properly.

Booking the same carrier for both outbound and return parts of your itinerary can sometimes be advantageous when "things go horribly wrong". For example, on my most recent itinerary, I got to my destination a full day late because of weather problems causing many flight cancellations. Since my entire itinerary was booked with United Airlines, I called and talked to their phone agent to request rebooking my return flights for a day later also so that I could spend the same amount of time at my destination. The phone agent checked with a supervisor, who authorized her rebooking me on roughly same-time flights a day later without paying any fare difference (which likely would have been expensive - it was already Wednesday July 29 when I called and I wanted to change to flights on Friday July 1, a day when most planes were going out full). Had I booked my return flights separately, e.g., with American Airlines, they would not have had any reason to be particularly sympathetic to me.

However, it is also the case that circumstances like the above are relatively rare, so I would certainly consider booking a mixed itinerary if that gave significant up-front dollar savings.