In a record-setting order that underscores surging demand in India for air travel, IndiGo airline said it is buying 500 passenger jets from European plane-maker Airbus.

India’s dominant carrier is buying the A320 aircraft in what the companies said on Monday was the single biggest purchase agreement in commercial aviation history.

Executives from both companies announced the deal on the opening day of the Paris Air Show, the world’s largest event focusing on aviation and space industry. They didn’t disclose how much the order was worth, but it would likely amount to tens of billions of dollars.

The purchase highlights how the two companies are “democratizing affordable air travel for millions of people in the world’s fastest growing aviation market,” Airbus Chief Commercial Officer Christian Scherer said in a statement.

New Delhi-based IndiGo’s order surpasses another mammoth deal signed months earlier by Air India for 470 aircraft from both Airbus and U.S.-based rival Boeing.

Indian airlines are racing to tap surging demand for travel from the nation’s growing ranks of middle-class consumers.

Airbus likes to unveil major jet orders at the air show held every other year in its home country. Airbus is one of France’s – and Europe’s – biggest companies, and its performance at the Paris air show is seen as important to its public image in France.