Ryanair announced today it would launch 13 new routes from Edinburgh this winter - so long as ministers cut air passenger duty (APD) as planned.
The routes are to Baden, Budapest, Carcassonne, Eindhoven, Hamburg, Katowice, Nantes, Prague, Szczecin, Toulouse, Venice, Valencia and Wroclaw.
All but Budapest, Hamburg, Prague and Venice are new for the airport.
Ryanair has previously flown between Edinburgh and Katowice, Szczecin and Wroclaw, and Jet2 used to fly to Toulouse.
It announced earlier this month new routes from Glasgow to Madrid and Krakow this winter.
Airline chief executive Michael O'Leary said some or all would be withdrawn if the Scottish Government did not halve the tax next year, as it intends.
However, the minority administration would have to win opposition support - most likely from the Conservatives - to get the plan through.
Labour, the Liberal Democrats and the Greens oppose the reduction.
Air passenger duty is charged at £13 per short-haul flight from UK airports.
Ministers plan to abolish it when they can afford to.
Mr O'Leary's announcement in Edinburgh also included extra flights to Copenhagen and Fuerteventura.
He said: "This is a demonstration to the Scottish Government of the benefits if they go ahead with the promised cuts in APD."
EasyJet, Scotland's largest airline, has previously said it would significantly increase flights if APD was cut.
Mr O'Leary, making at least his fifth visit to Edinburgh in two years, said he was "taking the bull by the horns" in announcing new routes ahead of the tax cut.
He was meeting First Minister Nicola Sturgeon this afternoon to underline the significance of the airline's move.
However, he warned: "If the Scottish Government does not go ahead, some of these routes will be withdrawn" - and won't continue into winter 2018.
"I think it will help them to get it through Parliament."
Ryanair has already announced five new routes for Edinburgh this summer, bringing its total to a record 38.
The planned winter schedule, which is traditionally smaller, will now equal that.
It is expected to increase the airline's annual passenger total at Scotland's busiest airport to 2.8 million, putting it second behind EasyJet.
Ryanair will have 17 routes from Glasgow, nine from Prestwick and two from Aberdeen this winter.
Edinburgh airport chairman Sir John Elvidge said: "The prospect of a reduction in APD has tipped the balance in favour of investment in Scotland."
Janice Hogarth, secretary of the Scottish Passenger Agents Association, which represents travel agents, said it "absolutely endorsed" Mr O'Leary's views on APD.
She said: "This is a massive opportunity if the Scottish Government fulfills what they say they will, both for outbound and inbound passengers."
But Scottish Greens co-convener Patrick Harvie said: “The Scottish Government would do well to ignore this obvious exercise in corporate flim flam.
When Ryanair announced a raft a new routes from airports down south just a few weeks ago, it did so without a threat to the government to change its air passenger policy.
"And when other places like Northern Ireland pursued a similar tax cut, it didn’t change the fundamental economics that determine whether a route is profitable or not.
“The policy of a tax cut for the aviation industry is being presented without any coherent evidence about the impact on jobs, on the economy, on ticket prices or on the climate change effects.
"I don’t think the SNP’s supporters would take kindly to their party’s leaders doing a deal with the Tories to force through this tax cut, which flies in the face of the evidence.”
Mr O'Leary also warned there is a remote chance of all flights between the UK and Europe being suspended in March 2019 if the UK Government opts for a "cliff-edge" Brexit.
The businessman said the current open skies arrangement hinges on recognising the jurisdiction of the European Court of Justice, which Prime Minister Theresa May said Britain would no longer be subject to.
Mr O'Leary believes it will take more than the two-year time frame from triggering Article 50 to put agreements in place with European Union (EU) nations.
He said: "In the airline industry we could be heading for a very difficult divorce with Europe.
"There is a possibility, unlikely, but nevertheless a possibility that there may be no flights between the UK and Europe in March 2019 if the UK walks off this cliff that they seem determined to walk off."