5320*14= 74480 gallons. 
 First let us convert gallons to cm^3 and we get 2.819374858x10^8 cm^3. 
 We then multiply with density and then times 1000 to get it in terms of tons. 
 Then multiply the number by 7 to get how many tons of crude oil a single plane uses in 14 hrs. 
 Finally divide this by the production of crude oil. 
I got 4737 airplanes.