I will fly on January to hometown. The flight is from Spain.
For the meal in the flight, they didn't show Halal Food, but my friend suggested me to take Kosher meal. Should I take it?
Yes, it is permissible for Muslims to eat Kosher meat. Allah says in the Quran (interpretation of the meaning):
Made lawful to you this day are At-Tayyibat [all kinds of Halal (lawful) foods, which Allah has made lawful (meat of slaughtered eatable animals, etc., milk products, fats, vegetables and fruits, etc.). The food (slaughtered cattle, eatable animals, etc.) of the people of the Scripture (Jews and Christians) is lawful to you and yours is lawful to them.
(Lawful to you in marriage) are chaste women from the believers and chaste women from those who were given the Scripture (Jews and Christians) before your time, when you have given their due Mahr (bridal money given by the husband to his wife at the time of marriage), desiring chastity (i.e. taking them in legal wedlock) not committing illegal sexual intercourse, nor taking them as girl-friends. And whosoever disbelieves in the Oneness of Allah and in all the other Articles of Faith [i.e. His (Allah's), Angels, His Holy Books, His Messengers, the Day of Resurrection and Al-Qadar (Divine Preordainments)], then fruitless is his work, and in the Hereafter he will be among the losers.
-- Quran 5:5