If it's a formerly used name, then it is no problem at all.
Actually, this might well be a problem.
Here are Sami's exact words on the subject from the manual:
"Historical airline names may be allowed if it is certain that the name is no longer owned by any other company; it is the responsibility of the user to check this. But generally past airline names (such as Pan Am) are not recommended. Please create your own custom airline instead."
Sami understandably doesn't want to be sued. If its been checked out by players using former names, great, but a caution seems appropriate.