Here, we've defined rockets to be cargo too....

(London PLACE)
(Paris PLACE)
(JFK PLACE)
(r1 ROCKET)
(r2 ROCKET)
(r1 CARGO)
(r2 CARGO)
(jason CARGO)
(mxf CARGO)
(avrim CARGO)
(alex CARGO)

(preconds
(at r1 London)
(at r2 London)
(at mxf London)
(at jason London)
(at avrim JFK)
(at alex JFK)
(has-fuel r1)
(has-fuel r2))

(effects
(at mxf Paris)  
(at avrim Paris)
(at jason Paris)
(at alex Paris))