The captain is at the controls, the tray tables are stowed, and nobody is smoking in the lavatories. We’ll be taking off shortly.

But wait, what about the coffee machines — are the coffee machines ready for departure?

Airlines blame flight delays on many things — missing paperwork, storms in faraway states, planes stacked up at La Guardia — but one explanation in particular trips up some travelers. It’s the broken coffee maker in the airplane galley. “Not sure why an @AmericanAir flight has to go back to the gate because of a freakin coffee maker...... that baffles me,” wrote Ryan Fahey on Twitter in February.

The miracle of human flight with onboard snacks is one of humanity’s great achievements. How is it, then, that a balky coffeepot can bring a jumbo jet to a dead halt?

It turns out to be a surprisingly complex problem to fix. An “inordinate amount of coffee maker problems” are causing short flight delays, the chief of operations for American Airlines, Robert Isom, said recently in a podcast for company employees. “If we can’t find a fix, we ought to just replace all the coffee makers.”