Atlanta-based Delta acquired 228 million additional shares in Aeromexico’s holding company under the oversubscribed offer that closed on 10 March, it says today. It now holds a 36.2% stake in the airline.

“This is yet another milestone that strengthens the Delta-Aeromexico relationship as we move toward implementing our joint cooperation agreement in the second quarter,” says Ed Bastian, chief executive of Delta, in a statement.

Aeromexico and Delta will launch an immunised joint venture covering their flights between Mexico and the USA on 1 April.

Delta paid Ps53 ($2.70) per share for the additional stake in Aeromexico under the offer that was launched on 13 February.

The US carrier has the option to acquire an additional 12.8% stake in Aeromexico Group for a 49% share in the airline.

Delta first disclosed plans to increase its stake in Aeromexico in November 2015. It initially invested $65 million in the Mexican carrier in 2012.