I think it depends on who you come across at the security check point. I fly out of LAX to asia every other month and several times I had checked in nitro cars, engines, and even a fuel gun once and never had a problem.
It is definately who you check in with. My friend came from Canada to Japan with an ek4 mt and radio already used. Tank had been cleaned. He brought it on as carry on! They made him turn it on and show that the electronics where for the servos and not a detonator, but the point is they let him on. It is all in who you get. (this was this summer) Then you have other people who wont even let you come over with foam tires? I dont get it?
Its all in the interpretation.