What caused the death of the following airmen killed on active service (Flight Global):

Sgt (Wop/Ag) Patrick F. CLARKE - 546660 - Flight Global: killed in action (while flying in operations against the enemy) - 254 Sqn (Blenheim - Sumburgh/Shetlands), buried Lerwick New Cem., Zetlandshire (UK8375), and

Sgt (Nav) Irving H. GUDDON - 741041, buried Medstead Cem., Hampshire (UK4873), and

Sgt (Pilot) Charles B. HAZEL - 517158, buried Southend-on-Sea (Sutton Road) Cem., Essex (UK3614), and

Sgt (Wop) James P ROSS - 625019, buried Urmston Cem., Lancashire (UK864), and finally

Sgt (Pilot) William R. SPEIR - 580985, buried Ayr Cem. (UK7699).

Aircraft losses for this day:

Anson I - K6272 - SAN - crashed on approach Adamton House, Monkton, Ayrshire
Audax I - K3093 - 7 FTS - crashed in forced landing Collingbourne Ducis, Wiltshire
Gladiator II - N5716 - FF Shetlands - crashed in forced landing Haroldswick, Unst, Shetlands
Hart Trainer - K6469 - 12 FTS - crashed on landing Grantham
Monospar ST-4 - X9367 - 6 AACU - crashed in forced landing Congleton, Cheshire
Oxford II - N4767 - 14 FTS - crashed take-off at night Cranfield
Shark II - K8901 - TTU - crashed in forced landing 2 miles NNE of Lochwinnoch, Renfrewshire.

Regards and thanks for your help.
Henk.