If I am flying on British Airways/ a Oneworld airline but does not have my BA(Silver) account number on my boarding pass/in the booking, can I still access Oneworld lounges by showing the silver status on my BA app?

I have done this at LAX, with no problems. Should be ok.

access to the one world lounges using the membership card is usually ok. A 3rd party airport lounge atvan outstation that a one world carrier has a contract with may be more problematic

My only experience of this was the woman on reception wrote down my BA number, because their scanner wasn't liking my BP for the life of it. Whether they 'charged' BA or not, I don't know. Thankfully they were well versed and understood entry rules, and recognised the silver membership instantly, and knew I could guest someone in as well. This was at the Toulouse lounge I believe.

If necessary, the other oneworld airline can call their internal oneworld helpdesk hotline, who can contact BA to verify your membership.

AS will give pushback if the computer says “no” when doing a BP scan at their lounges. They insist that only the FF account number on the BP can be used to determine access. We had an issue with access trying to enter the AS lounge at JFK. At the time, my partner’s OW status pulled up as Ruby, even though she was BA gold, so were refused access. She showed her BA digital card that indicated OWE. She was informed that she had to use the membership number on the BP and not the card. We explained that the number on the card DID match the number on the BP!

What was especially annoying is that prior to traveling, we knew of the Ruby issue, so had reached out to BA to tie up with the OW liaison desk and AS to let them know my partner was OWE and there was a note placed on the reservation.