There are also other airlines than BA and AA. Overall there are about 60000 enplanements[1] at McCarran airport every day. It seems implausible that 337 passengers (747 max pax load) could not be accommodated out of there to another hub (not necessarily of OneWorld) and then onto the UK within 24 hours. Or to their ultimate destination if they are only in transit at LHR.


[1] Don't blame me for the word, that's from https://www.mccarran.com/pubfile/b08...0190326-114151