By Aditya Kalra

NEW DELHI (Reuters) - The chief executives of Air India and Akasa Air have privately exchanged barbs over the poaching of pilots, with the latter accusing its bigger rival of rule violations, provoking a reply that collusion to curb job switching can breach competition law.

The exchange, detailed in a Sept. 21 letter seen by Reuters, spotlights growing competition in India's aviation market, as a strong rebound in air travel after the pandemic, coupled with a flurry of orders for new aircraft, lead to a shortage of pilots.

The rare verbal and written confrontations between the airlines' chief executives were detailed in the letter, sent by Campbell Wilson of Air India, which is owned by the Tata Group conglomerate, to Vinay Dube of low-cost airline Akasa.

It followed a telephone call between them and a missive Dube had sent expressing his concerns to the Tata Group.

The Sept. 21 letter shows Air India pushed back after Akasa accused it of contravening government policies that mandate a notice period of six to 12 months for pilots, rules that Indian pilots' groups are challenging in court.

Wilson told his counterpart the government rules were "not currently enforceable", adding that Akasa itself had "previously engaged in the same actions" by poaching pilots from Tata Group's budget carrier, Air India Express, and other airlines.

"It was a little surprising to us that Akasa now found the practice objectionable," Wilson wrote in the letter, which Reuters is reporting for the first time.

Akasa did not comment on its communication with Air India, but said the issue of pilot exits was "now behind us ... we are squarely back in growth mode".

Air India declined to comment and the two chief executives did not respond to requests for comment.

The dispute comes at the time of a hiring spree by Air India, with its arm, Air India Express, seeking to more than triple its fleet to 170 over five years.

In recent weeks, Akasa has lost about a tenth of its 450 pilots, who left without serving out notice periods, some to join Air India Express.

In September, Akasa said it feared a shutdown and sued some pilots, as well as the aviation watchdog, for not coming to its aid, in lawsuits still pending in the courts.

In his letter, Wilson added that he had "cautioned" Dube during their telephone call that asking a competitor to collude in curbing employees' rights to switch employers "could be construed as potentially a contravention of competition law".

"I regret that you interpreted my courtesy of taking your call and listening to your request as assent," he added.

The Federation of Indian Pilots has described the alleged mass resignations from Akasa as an "indication" of employee discontent, while India's aviation watchdog has said it cannot interfere in matters related to employment contracts.

India's newest airline, Akasa started flying in 2022, garnering a market share of 4%. It competes with IndiGo, which commands a share of 60% and Tata Group's airlines that together have a share of 25.7%.

In the Sept. 21 letter, Air India's Wilson expressed the hope that Akasa would make investments to "attract, retain and develop" its own staff, adding that his airline looked forward to "continuing healthy competition".