Ryanair boss Michael O'Leary has warned politicians that he needs Hangar 6 at Dublin Airport within two weeks before he moves 300 jobs elsewhere in Europe.
The airline chief executive told a cross-party delegation he was already in talks with two other governments about opening a new maintenance facility for his airline.
He said Tanaiste Mary Coughlan had to move swiftly to get Aer Lingus out of the hangar to secure the hi-tech positions.
Out-of-work engineers from the former SR Technics site earlier marched through Dublin city over their futures.
"If the Tanaiste wants these jobs, get us Hangar 6 within the next two weeks, and if you don't, I understand," Mr O'Leary said at an Oireachtas Transport committee where he appeared alongside Aer Lingus boss Christoph Mueller, Declan Collier, of the Dublin Airport Authority (DAA), and IDA Ireland's Barry O'Leary.
Labour TD Tommy Broughan accused the businessman of acting like a spoilt child and waving a rattle and throwing tantrums because he was not getting his own way.
Pressure has mounted on the Government since Mr O'Leary announced he could have created 500 skilled jobs in Dublin if he was given the facility when he first approached the Department of Enterprise more than a year ago.
The Ryanair boss maintains his only condition is that he would not deal with DAA, but stressed Ms Coughlan did little to intervene.
More than 1,000 workers lost their jobs when the SR Technics plant shut down.
In January Aer Lingus moved in as tenant and last night revealed plans to house a new centralised staff operations centre for Aer Lingus comprising maintenance stores, technical stores, operations control, flight operations and cabin operations.