What is the ruling on a technician working for an airline that serves alcohol to passengers, and is his money unlawful?

There is no harm in working in aircraft maintenance for planes that transport passengers, because the original work is permissible, which is transporting passengers from one place to another. This work is not rendered forbidden by the impermissible foods and drinks served on them.

This work would be forbidden if it involved assisting a transgressor in their transgression, such as maintaining a warplane that fights Muslims.