The only sentence that contains an adjective used in the...

A

"It is of course, and must remain, the most important aspect, ..." (lines 7-8).

B

"Having first guaranteed that airspace is less crowded −" (lines 24-25).

C

"... that the system is able to accommodate more traffic −" (lines 26-27).

D

"… operating hours are tending to become more restricted…" (lines 32-33).

E

"The 'Airports' pages ... will give you a very good general idea…" (lines 51-52).