The Chinese mainland on Wednesday defended its decision to adjust the flight path of the M503 flight route, saying it is necessary to ensure aviation safety and convenience for both sides of the Taiwan Strait.

The Civil Aviation Administration of China announced on Tuesday that it would cancel the M503 flight route's current north-to-south "offset" and also start using two connecting routes to fly from west to east onto the M503.

The move has been met with criticism from Taiwan, where the island authorities have accused the mainland of "ignoring flight safety" and "disrespecting Taiwan".

The M503 route is a civil aviation route decided by the mainland in the Shanghai Flight Information Region on the west side of the so-called median line of the Taiwan Strait in early 2015 and was moved several kilometers to the west of its original course later.

In a regular news conference on Wednesday, Chen Binhua, spokesman for the Taiwan Affairs Office of the State Council, said the M503 flight route falls within the Shanghai Flight Information Region. The route is necessary to ease air traffic congestion in the region and ensure safety, he said.

He also dismissed Taiwan's claims that the route change, which canceled its westward "offset measure", is a political move.

"The M503 flight route is a civil aviation route, and Taiwan is part of China. The so-called median line is non-existent," Chen said. "The route adjustment is a routine measure for civil aviation management and does not require consultation with the Taiwan side."

Chen also said the mainland has been working to facilitate cross-Strait travel. The mainland has resumed direct flights from 14 cities on the mainland to Taiwan, and the number of flights and passengers has increased. However, he said that more needs to be done.

"We hope the Taiwan authorities will lift their unreasonable restrictions to meet the travel needs of the people on both sides of the Taiwan Strait," he said.