I did LGW-LHR = 25.2 miles. But that's because a diversion.

I think you missed the point of the question. Staying aboard an aircraft making multiple stops on a milk run wasn't the point of the question as I interpreted it. I thought it was what was the shortest jet flight you've taken as a standalone flight (as a local O&D passenger).

For me, that's UA SFO-SMF. Flew that route many, many times as a local passenger though I only remember one of those flights being on a jet (UA 727)

I've flown SFO-OAK but not as a local passenger.

Yes, should have been more explicit and stated shortest (mainline) scheduled jet flight which takes one from O to D. Doesn't really make sense unless the surface transport alternative is relatively long and tedious and almost just as expensive, as it is for my route.

Not that I can see it ever happening but XSP-JHB on an A380 (since both the national airlines involved have or had them) - or just any jet - would be pretty cool. Time saver especially one weekends, or most weekday rush hours.

I was once on a scheduled seaplane flight in New Zealand - I think it lasted all of 10 minutes so must have been very short. If choppers are counted as flights some might be sub-15 miles.

My shortest commercial flight (and international) was on Gulf Air A320 Bahrain to Dammam. 50 miles and it took them 14 minutes. We were served meal before the take off and taxi :)
Second shortest flight was on United Express CRJ-200 Colorado Springs to Denver. Flight time 18 minutes (don't remember the distance).

COS-DEN is 73 miles

sub-100-mile entries from my log:

OK1937 PZY-BRQ on 05 Apríl 2017. Just under 100 km on A319. This was an anniversary flight for celebrations of 80 years of Prague airport (hence the flight number), the entire route was PRG-PZY-BRQ-PRG, but I only flew this one sector.

The flight was blocked at 30 minutes but it ended up even shorter as it was originally supposed to also include a low pass over LKZL which got cancelled because of bad weather.

https://cimg5.ibsrv.net/gimg/www.fly...49385282d2.jpg

BZN-BTM (80-something miles)
SWP-WVP (35 miles - private turboprop)
ISA-CNJ (50-something miles)

Nothing compared to most here, but 151 miles between LPB (La Paz, Bolivia) and RBQ (Rurrenabaque, Bolivia) on a CRJ-200 on Amaszonas (and vice versa). Blocked at 30 minutes, to drive between the two cities would be 10h40m according to Google Maps.

Good example of an itinerary where land-only travel would seem faster until one looks into the logistics. There must be other examples of city pairs served by mainline jet in the past (either because there were no regional jets or perhaps suitable turboprops for whatever reason). One such airport would be XKH (Phonsavan in Laos)

Handful of UA OAK/SFO in the mid to late 80s. Might have even been on a DC10. Took about 5:10 due to the two u-turns necessary!

Shortest jet segment: DTW-FNT / FNT-DTW (56 miles)

Shortest O&D segment: HNL-OGG / OGG-HNL (100 miles)

Shortest O&D segment in which there were other viable transportation options: SEA-GEG (224 miles)

LCY-STN, 27miles. Destination was Rotterdam but diverted due to weather.

Two other candidates for me:

162 miles from BMV (Buôn Ma Thuột, Vietnam) to SGN on Air Mekong's CRJ-900. Blocked at 50 minutes but the drive would take 7h45m.

186 miles from IXJ (Leh, Ladakh, India) to IXL (Jammu, Jammu & Kashmir, India) on an Air India A320. Blocked at 50 minutes but the drive would take 14h49m!!