In particular, the union said it wanted transparent systems for involuntary base transfers, command upgrades and the allocation of annual leave and promotion. "If it is not possible to immediately negotiate the introduction of such a Seniority Agreement, it is our intention to escalate this matter as a matter of urgency, to seek sanction for industrial action up to and including strike action should that be necessary," the letter said, setting a deadline of yesterday for positive response. Ryanair's Irish union, IALPA, two weeks ago threatened possible strike action unless the airline agreed to new working practices. BALPA national officer Terry Brandon told the Irish Independent that the union has now agreed a meeting with the airline next month where the issue will be on the agenda. A spokesman for Ryanair said the airline did not comment on negotiations with its staff. (Additional reporting by Reuters)