Flights in and out of Kenya's main airport are being delayed following a planned strike by aviation industry workers, the national airline and airports authority have said.

Departing flights from Nairobi's Jomo Kenyatta International Airport - one of Africa's busiest transport hubs - have been delayed by up to four hours.

Some passengers report they have remained seated on the aircraft for extended periods while pilots wait for clearance to take off.

In a statement, Kenya Airways said it was experiencing "air traffic control operational delays affecting certain departures and arrivals". It added that it was working with authorities to minimise disruptions and maintain safe operations.

"Passengers are advised to expect possible schedule adjustments, including delays," the airline said, while apologising for the inconvenience.

The disruptions follow a warning a week ago from the Kenya Aviation Workers Union (KAWU) of plans to strike over pay and poor working conditions.

KAWU Secretary-General Moss Ndiema told the Daily Nation that the strike began at 06:00 local time (03:00 GMT), affecting passengers and airlines nationwide.

"There's a big backlog. Planes are hardly leaving the airports," he was quoted as saying.

A Kenyan senator travelling from the western city of Kisumu said he had to travel by road due to the strike.

"This KCAA strike is really biting! Been forced to hit the road after many hours at the airport, waiting in vain," Boni Khalwale said on X.

"Passengers at JKIA are currently experiencing the true meaning of patience and character development," another Kenyan said, adding, "If you have a flight today, just carry a mattress because you might be living at the airport."

The Kenya Airports Authority (KAA) said it had activated contingency plans at the airport and has urged passengers to contact their airlines for updates.

Aviation sector workers blame the Kenya Civil Aviation Authority (KCAA) of stalling salary negotiations, delaying union remittances and discrimination.

They also accuse the authority's management of showing an unwillingness to resolve labour disputes that have persisted for more than a decade.

Last week, KCAA went to court seeking orders to halt the strike. A labour court judge suspended the action pending further directions due next week.

In a statement on Monday, KCAA said it was actively engaging the relevant parties "in line with applicable labour laws and court directions".

It added that "in light of the planned strike" it was activating measures to ensure aviation safety and service stability.

The main airport in Nairobi is one of the busiest hubs in the region and serves as a key gateway between the continent and the rest of the world. Last year, it handled about nine million passengers, according to Kenyan authorities.