Okay so i randomly went to search up on airlines (ok just turkish and KLM for obvious reasons) and i kind of found some information.

Flight to istanbul likely to fly planes made >2005. So that's 3 years old. Anyway this plane is really comfy to sit, it's the A330-200 which whoever went to prague last year, it was the same plane as that from dubai to vienna.

Flights to warsaw are on variety of planes from new to old so it really depends on your luck but the oldest can go back as far as 1989 or something i think but seriously 20 years for a plane isn't THAT old. There're many airlines flying older planes. SIA has planes that're 16 or so years old i think and the planes they sell off to other airlines who're happy to fly them =)

Okay for KLM flights to amsterdam are also on planes that're nice and new like >2003. The 777-200ERs woot which i hate flying because everywhere i go i seem to sit on them -.-

Flights to warsaw are like turkish also with variety of old to new and the oldest also the same as turkish like built around 1989 because guess what, they both operate the same type of planes (duh there's essentially only boeing and airbus around..) So haha okay don't think they're that much better/newer than turkish.

Oh and did you know? KLM was involved in the worst crash in history of aviation. :O
Omg, later we can't fly both then trip burst LOL.