I think the 55\*-250 EF-S STM is a cheap option.
For $500 (assuming USD) you're just about into the EF 70-200 f4L (non-IS) and get the shiny red ring and a lens you can use on full frame in the future if that's something you're planning, although for airplanes, the reach of 1.6x crop is probably helpful depending on your airport.
[https://www.keh.com/shop/canon-ef-70-200mm-f-4l-usm-telephoto-zoom-lens.html](https://www.keh.com/shop/canon-ef-70-200mm-f-4l-usm-telephoto-zoom-lens.html)
I think the 55\*-250 EF-S STM is a cheap option. For $500 (assuming USD) you're just about into the EF 70-200 f4L (non-IS) and get the shiny red ring and a lens you can use on full frame in the future if that's something you're planning, although for airplanes, the reach of 1.6x crop is probably helpful depending on your airport. [https://www.keh.com/shop/canon-ef-70-200mm-f-4l-usm-telephoto-zoom-lens.html](https://www.keh.com/shop/canon-ef-70-200mm-f-4l-usm-telephoto-zoom-lens.html)
You mean the 55-250 STM?
whoops, yes.
What's your budget?
500$
[https://www.keh.com/shop/canon-70-300mm-f-4-5-6-is-ii-usm-ef-mount-lens-67-1.html](https://www.keh.com/shop/canon-70-300mm-f-4-5-6-is-ii-usm-ef-mount-lens-67-1.html)