having lived on a airbase (PAF Minhas Airbase which i visit almost every year) i would say counting shelters is probably one of the most reliable ways of determining a air force inventory, not to mention RAF Leuchars which i can see from my house in Scotland
if i could i would give you a full run down of Kamra, but i wont, as after the last time i did it, terrorists used the internet to plan the attack on the airbase, so in the interest of security i will leave it there
At the very least it helps establish an upper value for the number of aircraft in service or to be procured, even if not immediately so.