Stinsy wrote: ↑Sat Sep 25, 2021 12:23 pmTowing aircraft to the runway has been tried a few times to save fuel (whenever the price of oil peaks) but has been discounted because of safety. Running the jet engines under load for a few mins while taxiing is a good way to allow problems to show themselves before takeoff is attempted.
Umm... not exactly. For short trips (typical EasyJet/Ryanair operational modes) they spend a very big chunk of the total flight on the ground, far more than required for an engine test. It isn't just fuel either - engine run hours mean increased maintenance spend.
The real problem is that you're adding quite a bit of weight and inertia to the wheels - that reduces payload, increases fuel burn in flight and increases tyre wear. There's a financial improvement (largely from reduced ground staffing costs - you don't need a tug driver to push back from the terminal any more, just a banksman), but not enough to justify the development and certification costs.
