Other planes look small

[Jotaele]

LOL, it really looks like a RC model in your pic.I can be caused due to the low setting you are using, there are not textures that helps like reference. In computers like has been explained previously, its very dificult to juzge sizes if you are not using 3d glasses due that you dont have stereographic view.
Other cause could be that due to the low settings , game is using a LOD that does nnot have the correct size.
Is very strangle that being both planes in land, your head ant the other spitfire pilot head, should be aligned with horizont, so it seems that the other plane is really smaller.