Ruling on working as an engineer for an airline, when his work includes playing music and video clips; what is the ruling on his salary?

Firstly:

It is well-known that songs, music and indecent movies are
things that are prohibited in our Islamic religion, because of what they
contain of things that corrupt people’s religious commitment and morals.

We have explained that previously in several answers. Please
see the answers to questions no. 5000,
85232, and 125535.

Secondly:

If something is prohibited, such as music, smoking, watching
indecent movies, and the like, then it is not permissible to work in that
field or to help with it in any way whatsoever, whether that is by
manufacturing equipment that is used for such purposes, or maintaining it,
or selling it, and so on, because that comes under the heading of helping in
sin, encouraging it and approving of it. Allah, may He be exalted, says
(interpretation of the meaning):

“Help you one
another in Al-Birr and At-Taqwa (virtue, righteousness and piety); but do
not help one another in sin and transgression. And fear Allah. Verily, Allah
is Severe in punishment”

[al-Maa’idah 5:2]

“They will
bear their own burdens in full on the Day of Resurrection, and also of the
burdens of those whom they misled without knowledge. Evil indeed is that
which they shall bear!”

[an-Nahl 16:25].

And the Prophet (blessings and peace of Allah be upon him)
said: “Whoever sets a bad precedent in Islam and it is acted upon after him,
a burden of sin will be recorded for him like that of those who do it,
without that detracting from their burden of sin in the slightest.” Narrated
by Muslim (1017).

See also the answers to questions no.
112902, 134169 and 34597

Our advice to you is to strive to make sure that your
provision is halaal and wholesome, and to look for another job in a
permissible field in which you do not have to work in or help with any
haraam activities. Whoever gives up something for the sake of Allah, Allah
will compensate him with something better than it.

Ahmad (19813) narrated that Abu Qataadah and Abu’d-Dahma’
said: We came to a man of the desert and said: Did you hear anything from
the Messenger of Allah (lettings and peace of Allah be upon him)? He said:
Yes, I heard him say: “Verily you will never give up anything for fear of
Allah, may He be glorified and exalted, but Allah will give you something
better than it.”

Al-Haythami (may Allah have mercy on him) said: Its men are
the men of as-Saheeh. End quote from Majma‘ az-Zawaa’id wa Manba‘
al-Fawaa’id (11/207)

Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) was
asked:

I work in a movie theatre, and my work is running and
watching the projectors. Sometimes they show some indecent and inappropriate
movies, and for that reason I am not happy with this job, but I cannot find
any other job, even though I feel that I am carrying a heavy burden of sin
because of it. What do you think I should do? What do you advise me to do?
What is the ruling on my previous earning from this job?

He (may Allah have mercy on him) replied:

You should not work in this job, because it is haraam and
corrupt, and causes corruption. What you have to do is leave it and look for
provision through another job. Allah, may He be glorified and exalted, says
(interpretation of the meaning):

“and
whosoever fears Allah and keeps his duty to Him, He will make his matter
easy for him”

[at-Talaaq 65:4]

““And
whosoever fears Allah and keeps his duty to Him, He will make a way for him
to get out (from every difficulty)”

[at-Talaaq 65:2]

“O you who
believe! Keep your duty to Allah and fear Him, and speak (always) the truth.

He will direct you to do righteous good deeds and will
forgive you your sins”

[al-Ahzaab 33:70-71].

Whoever gives up something for the sake of Allah, Allah will
compensate him with something better than it, and the provision that Allah,
may He be exalted, provides should not be sought through haraam means. So
you have to leave this job immediately, and seek provision elsewhere. There
are many ways of making a living, praise be to Allah. With regard to what
you have earned of these haraam earnings, if you were unaware of the ruling
when you started this job, and you did not know that it was haraam for you,
then you do not have to do anything, because you acquired it in ignorance,
and it did not involve consuming the wealth of anyone else unlawfully. But
if you give in charity the equivalent of what you earned for running the
haraam movies, then this is better. And Allah knows best.

End quote from Fataawa Noor ‘ala ad-Darb

See also the answer to question no.
106925

And Allah knows best.