Congrats sq380 on ur new dslr!
I guess we both share the same interest - I'm pretty much into aviation photography too
Will I see you more often at Changi Airport? Haha.
Well from my experience with 55-250mm lens, the distortions are very minor but vignetting is a problem. Especially evident if you got strong sunlight in the morning/afternoon etc. Try to shoot at F8 or F11. It will be good
And what I felt is 250mm will be sufficient if you are large jets, like B74X, A380, A34X, these planes have either long bodies or long wings.
But for smaller ones, like A32X, B73X, maybe you will a...little more zoom. Especially if they are already up in air.
For planes at the aprons (unless u are at the viewing mall), then 250mm to me sometimes will not be enough. Consider longer focal lengths lenses, if you have the money
Say, 70-300mm? 100-400mm? Or Sigma's 50-500mm! WOW~! Haha.
The best things in life are free.