We usually go to Vegas 3/4 times a year and pretty much take the same flights time out of DFW. I noticed the other day the flight times have increased by 45 minutes or more. Are airlines doing this so they can still claim they are "on time"? Flights back from Vegas are usually under 2 hours, but they listing 2:45+. No biggie, just thought it was interesting

Partly that... also partly because it includes boarding and taxi time.

Example, I just flew SEA-BNA.
Actual flight time was ~3.5hours, but with boarding and taxi it was about 4-4.5.
(We caught good winds).
Normal flight is about 4-4.5hrs and Alaska had it showing 5ish hours.

American is adding more flight banks at DFW so they're adjusting the block time (from pulling the blocks around the tires upon departure to putting the blocks back upon arrival) accordingly. It'll take roughly the same time in the air.