Showing Aircraft

I need help. I don't know if I am not looking at the specs right, but if I try to send a large plane on a route and I "show aircraft" they don't appear. Things I already tried are as follows:

1) The planes do have available 140 hours.

2) They are not out of range.

3) They are not on any other routes.

4) I already tried to select idle plane from show aircraft menu.

5) I also tried to go to aircraft and select add route.

Help is appreciated. Thanks!