I work as a technician in a company that transports passengers by air, and this company serves alcohol to the passengers. Please note that my work is technical, repairing seats and everything that has to do with the airplane. Am I a party to their sin? Is my wealth haraam? Please note that I asked a shaykh in our country and he told me that I am very far away from haraam.
There is nothing wrong with working on maintenance of the airplanes that transport passengers, and this work is not rendered haraam by the haraam foods and drinks that may be served on board, because the work itself is permissible, which is transporting passengers from one place to another. And this is something that comes under the heading of necessity for many people.
The airline company and the passengers should also refrain from what Allah has forbidden.
Maintenance only becomes haraam work if it is helping a sinner to commit sin, such as working on maintenance of military aircraft for a state that is at war with the Muslims… and the like.
And Allah knows best.