Three more Ensigns - Egeria, Elsinore and Euterpe - were completed by Christmas 1938, and were dispatched to Australia with the holiday mail. All three suffered mechanical problems and did not reach their destination; consequently, all five Ensigns were removed from active airline service and returned to Armstrong for improvements. Reliability was improved, and more powerful (935 hp) Armstrong Siddeley Tiger IXC engines aided performance somewhat. The aircraft were delivered back to the airline starting in June 1939 along with the sixth to be built.
The plan to use four Ensigns with Indian Trans-Continental Airways, operating from Calcutta, did not come to pass due to the modifications and the onset of war although registrations and new names had been made and, in one case, painted on the aircraft.
Eleven aircraft were in service at the outbreak of the Second World War, with a 12th following soon after, and all were withdrawn in October 1939; they were to be camouflaged before flying a new route from Heston Aerodrome to Le Bourget Airport, Paris. The aircraft remained in service after formation of BOAC that November but instead of being taken up for military service remained civilian under direction of National Air Communications. Their first duties following the German invasion of the Low Countries was ferrying supplies to France. This was followed by evacuation before France capitulated in June. Despite operating away from their maintenance base for weeks at a time, Ensigns managed 100% availability and impressed with their short take-off run even when fully loaded.
Three Ensigns were destroyed by enemy action in 1940 (G-ADSX Ettrick and G-ADSZ Elysian in France, and G-ADTC Endymion at Bristol Whitchurch in November 1940). G-ADSX Ettrick, which had been abandoned at Le Bourget after being damaged by bombs on 1 June 1940, was rumoured to have been used by the Germans, and later given Daimler-Benz engines. This is considered by most experts on the Luftwaffe to be a myth which may have its roots in a Flight article by P.W. Moss in 1957. However, the Database section in the March 2015 edition of Aeroplane Monthly states that the Germans may have fitted Daimler-Benz engines to G-AFZV Enterprise.
As the aircraft were found to be lacking in performance, it was decided to give the remaining eight aircraft Wright Cyclone G.102A engines.
The final two aircraft that had been ordered by Imperial in 1936 were equipped with more powerful Wright Cyclone geared radial engines and completed as A.W.27A Ensign Mk 2s. The new engines significantly improved performance and allowed the Ensign to be used in hot climates and at high altitude. At the same time other modifications were incorporated and the prototype Mark 2, Everest first flew in June 1941, with Enterprise following at the end of October
All eight surviving airframes were upgraded with these newer engines in 1941-43, as they were completed they were transferred to the Middle East and worked for BOAC on Africa to India routes.
Ensigns flew throughout the war. On a ferry flight to west Africa, following trouble with her engines "Enterprise" made a force landing in the desert in French West Africa (at that point under Vichy France control) about 300 miles short of their destination. Codebooks and other paperwork on board was destroyed except that required to show the crew were civilian. They were picked up by an RAF Sunderland flying boat and taken on to Bathurst in Gambia. Enterprise was found by the French authorities, repaired and used as a hospital plane at Dakar before being flown to Vichy France. (During her service with the French, Enterprise was initially registered as F-AFZV, later becoming F-BAHD). After the German occupation of Vichy France, she was taken by the German Air Ministry and tested before being used as transport for officers. It was scrapped in Toulouse in 1943. Several were broken up for spare parts to support the remaining fleet.
From 1944 under the end of their service, the Ensigns were used between Cairo and Calcutta. When taken out of use for their Certificate of Airworthiness overhauls, the camouflage dope - which in combination with the heat had been rotting the fabric surfaces - was removed and thereafter the Ensigns were in a "natural" finish.
After the end of the war, due in part to their performance and the problematic maintenance of the fabric surfaces, it was decided eventually to remove the Ensigns from service and to return them to the UK. Euterpe which had been out of use since February 1945 was sacrificed to make repairs to the others.
The final Ensign passenger flight took place in June 1946 when Eddystone flew from Cairo to Hurn via Marseille; she had been delayed in the Middle East by repairs. Conversion of the Ensigns was considered and they were offered for sale but the projected costs were too much for those who showed interest. The aircraft were broken up at Hamble in March and April 1947 and removed to Cowley, Oxford where they were reduced to scrap.