Utilize the input text as a context reference, choose the right relationship between British Airways and London from the options. Options: 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.

MONTREAL, July 29 (Reuters) - A British Airways flight from Las Vegas to London made an emergency landing in Montreal early on Wednesday due to concern that a bomb threat had been made, an airport spokesman said.

Answer: headquarters_location