Data Point.

AY. LHR - HEL - HKG. Business Light.

BA number on booking. Checked in online. E boarding pass with BA number. Needed BA number (OWE) for bag allowance.

Checked in at LHR as usual. After bag dropped, asked check in agent to change BA number to MH number (no status). Paper boarding pass with MH number as evidence.

Used BA number E boarding pass for fast track and CX F lounge. Success.

Made a mistake of using BA number E boarding pass rather than paper boarding pass at gate to board (all these changing back and forth became too confusing!). Only realised this mistake when there was meet and greet onboard!

A few days later miles still were credited to MH! So it was a success.

Helsinki lounge - used BA e boarding pass to go in. Success.

Return - online check in refused to let me change it back to BA number. Went to HKG airport to check in. No need to ask for change to BA number and it still allowed me free check in bag with MH number (no status) on the boarding pass. Seat selection also remained. Don’t know why.

Went into CX F lounge with MH number boarding pass. Showed BA Gold card. Success.

Still waiting to see if the miles for the inbound will go to BA or MH. Watch this space.