Airlines sometimes turn their planes around and fly thousands of miles home when they have problems. Here's why.

• Airlines take into account safety and cost when deciding how to divert flights.
• British Airways typically sends flights back to London when possible, making repairs and rerouting easier.
• American Airlines has an automated tool called HEAT that helps it make calls on where to divert.

Plane diversions can be a nuisance for passengers and costly for airlines, especially if they end up back where they started in a so-called flight to nowhere.