Delta Air Lines (DAL) said on Monday that it has completed its purchase of a 49 percent stake in British airline Virgin Atlantic and added the two carriers plan to start cross-selling seats on each other's flights in July.

The U.S. Department of Justice and European Commission approved Delta's purchase of the Virgin stake last week. Clearance is still needed from the U.S. Transportation Department, and the companies said they expect that approval to come later this year, clearing the way for their transatlantic joint venture to start in the first quarter of 2014.

Atlanta-based Delta announced in December it would buy the 49 percent stake in Virgin Atlantic from Singapore Airlines. Virgin founder Richard Branson will keep his 51 percent share.

The Virgin venture will allow Delta to expand access at London Heathrow, a key international business airport where gate constraints have limited growth. A venture between British Airways <ICAG.L> and AMR Corp's <AAMRQ.PK> American Airlines currently dominates travel between the United States and London.