What is the ruling on wearing a cross in order to conceal one’s identity in the airport?

Firstly:

The cross is one
of the obvious symbols of disbelief, as Ibn al-Qayyim (may Allah have mercy
on him) said in Ahkaam Ahl adh-Dhimmah (3/1240). Therefore there was
no difference of opinion among the scholars that it is prohibited to wear
it.

It says in
al-Mawsoo‘ah al-Fiqhiyyah al-Kuwaitiyyah (12/88): It is not permissible
for the Muslim to make a cross and it is not permissible for him to issue
instructions for a cross to be made. What is meant is making a cross that is
symbolic of the crucifixion, and he should not keep it, whether he wears it
or sets it up, or he does neither.

Many of the
scholars have clearly stated that the one who does that is a disbeliever.

It says in
al-Fataawa al-Hindiyyah, one of the books of the Hanafi madhhab (2/276):
A person becomes a disbeliever if he puts a Zoroastrian cap on his head,
according to the correct view, except in the case of necessity to protect
himself from heat or cold; or if he puts a zunnaar [a kind of belt that was
worn by non-Muslims in the past] around his waist, unless he does that by
way of deceit at a time of war or he is acting as a scout ahead of the
Muslim army. End quote.

It says in Majma‘
al-Anhur fi Sharh Multaqa al-Abhur, which is also a Hanafi book (1/698): A
person becomes a disbeliever if he puts a Zoroastrian cap on his head,
according to the correct view, except if it is  for the purpose of freeing a
Muslim prisoner or it is a case of necessity to protect himself from heat or
cold, according to some scholars. End quote.

Al-Qaadi ‘Iyaad
said: Similarly, we regard as a disbeliever anyone who does any action that
the Muslims are unanimously agreed can only come from a disbeliever, even if
the one who does it openly professes Islam, yet he does that action…

… Such as
prostrating to an idol, or to the sun or moon, or to a cross, or to fire, or
going to churches and synagogues with their congregations, or wearing their
garments, such as wearing their zunnaar (distinctive belts) or cutting the
hair in the style of a monk (tonsure).

The Muslims are
unanimously agreed that such things are only done by a disbeliever, and that
these actions are symbols of disbelief, even if the one who does them openly
professes Islam.

End quote from
ash-Shifa bi Ta‘reef Huqooq al-Mustafa – Mahdhoof al-Asaaneed
(2/611).

The scholars of
the Standing Committee for Issuing Fatwas were asked about the ruling on
wearing a cross and they replied:

If the ruling on
wearing a cross is explained to him, and he is told that it is a symbol of
the Christians and is an indication that the wearer is content to be
regarded as one of them and that he is content with what they believe in,
yet he persists in that, he is to be deemed a disbeliever, because Allah,
may He be glorified and exalted, says (interpretation of the meaning):

“O
you who believe! Take not the Jews and the Christians as Auliyâ’ (friends,
protectors, helpers), they are but Auliyâ’ of each other. And if any amongst
you takes them (as Auliyâ’), then surely he is one of them. Verily, Allâh
guides not those people who are the Zâlimûn (polytheists and wrong-doers and
unjust)”

[al-Maa’idah
5:51].

If zulm
(wrongdoing) is mentioned in general terms, then what is meant is major
shirk and by doing that he is indicating that he agrees with the Christians
in their claim that ‘Eesa (peace be upon him) was killed, but Allah, may He
be glorified, has denied that in His book, where He says (interpretation of
the meaning):

“but
they killed him not, nor crucified him, but the resemblance of ‘Īsā (Jesus)
was put over another man (and they killed that man)”

[an-Nisaa’
4:157].

Shaykh ‘Abd
ar-Rahmaan al-Barraak (may Allah preserve him) said: The cross is well-known
to be the idol of the Christians in their churches and in their homes, and
they wear it around their necks and on their chests. Hence it is the symbol
of Christianity, and it is prohibited for the Muslim to wear it.

If a Muslim
wears it in order to appear to be a Christian, then this is a way of
expressing his approval of the Christians in their religion, and approving
of the Christians in their religion constitutes disbelief in Allah, except
in the case of one who fears for his life, in which case he is regarded as
being under compulsion, and Allah, may He be exalted, says (interpretation
of the meaning):

“Whoever
disbelieved in Allâh after his belief, except him who is forced thereto and
whose heart is at rest with Faith…”

[an-Nahl 16:106].

With regard to
one who wears a cross out of ignorance, then he is excused because of his
ignorance.

With regard to
one who wears it to please the Christians, that is prohibited and there is
the fear that it may come under the heading of disbelief in Allah… What the
Muslim must do is beware of that which Allah has prohibited. There is no
doubt that it is one of the most serious kinds of imitating the
disbelievers, and the Prophet (blessings and peace of Allah be upon him)
said: “Whoever imitates a people is one of them.” Narrated by Abu Dawood
(4031). So what he must do is beware of that, and we ask Allah to keep us
safe and sound. And Allah knows best. End quote.

http://ar.islamway.net/fatwa/8605

Based on that,
if the Muslim referred to in the question was compelled to do this, in the
sense that he feared that he might be killed or imprisoned if he did not do
that, then there is no blame on him in sha Allah, so long as when he did
that his heart was at rest with faith.

But if the
situation has not reached the point of compulsion and having no other
choice, then it is not permissible for him to do that.

It is essential
to differentiate between the situation of one who has been compelled to flee
from his country and the situation of one who is compelled to wear a cross.
He may have been compelled to flee from his country in order to escape being
killed or imprisoned, but wearing a cross is not something that he is forced
to do, because even if he did not wear it, he would not be subjected to
killing, imprisonment and the like.

This is a matter
concerning which one should be careful and understand the case of necessity
in which such concessions are granted, and cases in which there is no such
necessity.

Moreover, if he
is patient and does not make an outward show of symbols of disbelief, or
utter words of disbelief, this is better, even if he does fear for his life.

Making an
outward show of symbols of disbelief in the case of necessity which makes
such things permissible is a concession that is granted and there is no
obligation to avail oneself of it; rather firm resolve is better than that.

With regard to
fleeing for the sake of one’s religious commitment and one’s life, for fear
of fitnah (persecution) or death, this is something that is prescribed in
Islam and is either recommended or obligatory, according to the situation.

And Allah knows
best.