What is the relationship between Heathrow hub and London in the context of the input sentence. Choose an answer from: product/material produced; manufacturer; distributed by; industry; position held; original broadcaster; owned by; founded by; distribution format; headquarters location; stock exchange; currency; parent organization; chief executive officer; director/manager; owner of; operator; member of; employer; chairperson; platform; subsidiary; legal form; publisher; developer; brand; business division; location of formation; creator.

A clue to BA's lingering love affair with the 747 lies in the model's ability to eke out capacity from scarce operating slots at its London Heathrow hub at a time when lower fuel prices make retaining older planes an option.

Answer: headquarters_location