Transport Minister Dinh La Thang has suspended leave for employees of Vietnam Airlines, the top airliner in Vietnam, due to concerns about air safety.

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The minister asked the Civil Aviation Authority to delay applications for leave and ordered Vietnam Airlines to find ways to improve salaries and bonuses by the end of March 2015.

In October 2014, more than ten pilots submitted letters of resignation, and a large number of employees, including pilots, air traffic controllers and maintenance workers, have also attempted to resign. Salary was a major issue.

According to local pilots, their salary is about VND80m (USD4,000) per month, while equally qualified foreign pilots' with the airline earn from USD8,000 to USD13,000.

Vietnam Airlines argued it did not have to pay to train foreign pilots. It said basic training cost some VND2.5bn per pilot. The airline is the only Vietnamese carrier with the capability of training pilots. Pilots have to commit to work for at least 15 years to cover the cost of their training.

The airliner now has 600 local pilots, who account for 70 percent of cockpit crew.

In 2013, employees at Vietnam Airlines Engineering Company attempted to leave after the budget carrier VietJet Air offered them triple wages.

VAECO drew up a new contract in which employees must work at the company for 10 or 20 years. If they want to leave they would have to repay at least VND500m to cover their training fees.