The greatest disadvantage of the airship is size, which is essential to increasing performance. As size increases, the problems of ground handling increase geometrically. As the German Navy changed from the P class of 1915 with a volume of over to the larger Q class of 1916, the R class of 1917, and finally the W class of 1918, at almost ground handling problems reduced the number of days the Zeppelins were able to make patrol flights. This availability declined from 34% in 1915, to 24.3% in 1916 and finally 17.5% in 1918.