Airlines need staff to fly and maintain their aircraft. They need to pay applicable taxes and gate fees. They need to buy new planes, repair worn-out parts, manage their company pension plan, and everything else a service industry has to do. But by far, the largest chunk of their non-payroll operating budget goes to fuel. That's what costs the most for any given flight.
Andy WeirProblem is (follow me closely here, the science is pretty complicated), if I cut a hole in the Hab, the air won't stay inside anymore.
Andy WeirDesigning a station with artificial gravity would undoubtedly be a daunting task. Space agencies would have to re-examine many reliable technologies under the light of the new forces these tools would have to endure. Space flight would have to take several steps back before moving forward again.
Andy Weir