Details about the solution

After 45 minutes, or one-eighth of the way around,each plane has 135 kiloliters left.Orokana gives 45 to the professor and 45 to Fugōri,fully refueling them both.With her remaining 45, Orokana returns to the airport and heads to the lounge for a well-deserved break.45 minutes later, with one-quarter of the trip complete,the professor and Fugōri are both at 135 kiloliters again.Fugōri transfers 45 into the professor's tank,leaving himself with the 90 he needs to return.