Noun used as an adjective

Question:

In the following example, should the word flight be written with an s at the end?

• Flight Numbers AB123 and CD456 are now ready for boarding.

Answer:

In your example, the word flight remains in the singular because it functions as an adjective modifying the noun numbers. According to the Handbook for Writers, nouns used as adjectives do not change unless they are in the possessive form, in which case they are followed by 's (e.g. the flight's passengers).