Based on the images provided, you have a commemorative flight cover and its corresponding information card honoring the 70th Anniversary of the Battle of the Somme (1916–1986).

Front of the Flight Cover

The top half of the first image shows the commemorative envelope (cover). It features:

Central Illustration: Depicts four historical aircraft used by the Royal Flying Corps (RFC), including the Bristol Scout, Morane-Saulnier N, Nieuport 17, and De Havilland DH.2.

Postmark: A special commemorative handstamp dated 18 NOV 86 from the "British Forces 2114 Postal Services".

Postage Stamp: A 29p stamp featuring Lord Trenchard (the "Father of the RAF") and a De Havilland DH.9A bomber, issued as part of the 1986 Royal Air Force Commanders series.

Signatures: It is hand-signed by Squadron Leader Ian Mortimer, who piloted the flight.

Flight Details: The text on the right indicates this cover was flown in a Harrier GR.5 (serial number XZ 993) of No. 1 Squadron on a low-level mission over the Yorkshire Dales on November 18, 1986.