service ceiling vs combat ceiling

service ceiling and combat ceiling both are nouns.

Word	Noun	Adjective	Verb	Adverb
service ceiling	Yes	No	No	No
combat ceiling	Yes	No	No	No

As nouns, service ceiling and combat ceiling are synonyms defined as:

service ceiling and combat ceiling: altitude above which a plane cannot climb faster than a given rate

service ceiling (noun)	combat ceiling (noun)
altitude above which a plane cannot climb faster than a given rate	altitude above which a plane cannot climb faster than a given rate