British Airways has started disciplinary proceedings against three shop stewards following August's unofficial strike at Heathrow Airport.
At the time, baggage handlers walked out for two days in sympathy with sacked workers at the airline's in-flight caterer Gate Gourmet.
British Airways said two of the shop stewards have been suspended on full pay while the third continues to work.
All three are members of the Transport & General Workers' Union (T&G).
A spokesman for the T&G confirmed that disciplinary action has started against three of its members, but declined to comment further.
The BA baggage handlers went out on wildcat strike after Gate Gourmet's loss making UK division sacked 667 workers at Heathrow in a dispute over working practices and the hiring of temporary staff.
The BA walkout left more than 100,000 passengers stranded and cost the airline an estimated £40m ($72m).
Following the dispute, BA set up a confidential phone line as part of its investigation. Employees were invited to ring the number to report any incidents of alleged bullying or intimidation that led to the strike action.
The three union officials now being probed were reportedly named by staff calling the hotline. BA said it could not give out anymore information as the investigation was ongoing.
Negotiations are continuing to end the Gate Gourmet dispute, with all staff - including those that were sacked - having been offered redundancy packages.
About 700 staff - 300 of those sacked and 400 from current employees - have applied to accept the offer, according to the T&G.
Yet one area of disagreement appears to still need to be resolved - Gate Gourmet's insistence that it will definitely not re-employ 200 so-called "troublemakers".
While the US-owned caterer has secured the improved BA contract it says its UK operation needs to secure its financial survival, but this is dependent upon Gate Gourmet resolving the labour dispute.