Improvements which were effected in signalling arrangements between ships and aircraft were instrumental in adding greatly to their efficiency, and by the early summer of 1917 aircraft had commenced to play an important part in the war against submarines and in the protection of trade.

Thereafter progress became rapid, as the following figures show: 

In June, 1917, aeroplanes and seaplanes patrolling for anti-submarine operations covered 75,000 miles, sighted 17 submarines, and were able to attack 7 of them.

In September, 1917, the distance covered by anti-submarine patrols of aeroplanes and seaplanes was 91,000 miles, 25 submarines were sighted, of which 18 were attacked.

In the four weeks ending December 8, 1917, in spite of the much shorter days and the far less favourable flying weather experienced, the mileage covered was again 91,000 miles; 17 submarines were sighted, of which 11 were attacked during this period.

As regards airships the figures again show the increased anti-submarine work carried out: 

In June, 1917, airships engaged in anti-submarine patrol covered 53,000 miles, sighted and attacked 1 submarine.

In September, 1917, they covered 83,000 miles, and sighted 8 submarines, of which 5 were attacked.

In the four weeks ending December 8, 1917, they covered 50,000 miles, sighted 6 submarines, and attacked 5 of them.

The airships were more affected by short days, and particularly by bad weather, than the heavier than air craft, and the fact that they covered practically the same mileage in the winter days of December as in the summer days of June shows clearly the development that took place in the interval.

During the whole of 1917 it was estimated that our heavier than air craft sighted 135 submarines and attacked 85 of them, and our lighter than air craft sighted 26 and attacked 15.  The figures given in Chapter IX of the number of submarines sunk during the war by aircraft (viz. 7 as a minimum), when compared with the number of attacks during 1917 alone suggest the difficulties of successful attack.

In September, 1917, as extensive a programme as was consistent with manufacturing capabilities, in view of the enormous demands of the Army, was drawn up by the Naval Staff for the development of aircraft for anti-submarine operations during 1918.

The main developments were in machines of the large “America” type and heavy bombing machines for attacking enemy bases, as well as other anti-submarine machines and aircraft for use with the Grand Fleet.

Included in the anti-submarine operations of aircraft during 1917 were the bombing attacks on Bruges, since the German submarines and the shelters in which they took refuge were part of the objective.

These attacks were carried out from the aerodrome established by the Royal Naval Air Service at Dunkirk.  During 1917 the Naval Air Forces of the Dover Command, which included the squadrons at Dunkirk, were under the command of Captain C.L.  Lambe, R.N., and the operations of this force were of a very strenuous character and of the utmost value.