Just a reminder, planes can go over walls!

Or US citizens for that matter? Also, planes flying over the border aren't very inconspicuous.

I'm not saying they own a plane I'm saying they can board a plane, it would be pretty easy to just "take a vacation" somewhere and just stay there without going home.

They have to go thru Customs and have a passport or Visa...Hell , I have to have one to drive to Alaska thru Canada !

Work visa. At least 40% of illegal immigrants use a plane and have a work visa.