Given the input sentence, please extract the subject and object containing a certain relation in the sentence according to the following relation types, in the format of "relation1: word1, word2; relation2: word3, word4". Relations include: 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.

British Airways declined to specify how long the upgrade will prolong the 747's lifespan, though it has said the bigger 787 variants and Airbus's largest A350 will be used to phase out some jumbos through 2023.

Answer: operator: A350, British Airways