Talks between BA and Amadeus were still continuing as the deals the airline has signed with the three other GDSs came into force this week.
Under the three year agreements, BA will provide full content to Galileo, Sabre and Worldspan.
Agents using any of these three GDSs can join their opt-in schemes and receive "preferred channel" status to get full access to the BA inventory.
While no details of the deals with Sabre or Worldspan have been released, under the agreement with Galileo, the largest GDS in the UK and Ireland, BA will impose a surcharge of 50p per segment on first, business and economy fares and £1 per segment on its cheaper fares.
This new surcharge and any similar surcharges for Sabre and Worldspan agents were payable from April 10 when the agreements came into force.
No details of whether BA won a cut in its booking fee paid to the GDSs - and if so by how much - has so far emerged.
Amadeus which has not signed a deal with BA now faces a £3 per segment surcharge on all bookings made by its agents.
The Madrid-based GDS has told its agents that it will re-imburse this surcharge until May 1. After that the situation will be reviewed.
In a letter to its agents, Amadeus said it was still negotiating with BA and added: "It is still very much our desire to reach agreement with British Airways and to this end we have presented a number of competitive proposals."
BA confirmed that the talks were continuing.
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