On Saturday, British Airways abruptly suspended all flights to Cairo for seven days, citing unspecified security concerns.

Lufthansa also said it had cancelled flights to the Egyptian capital while an evaluation of the situation was taking place but later said normal flights would resume on Sunday.

Lufthansa flight 582 arrived on Sunday in Cairo from Frankfurt after a 90-minute delay, sources at Cairo airport said.

"It is an Airbus 330 that seats more than 350 passengers to make up for Saturday's cancellation," an official said on condition of anonymity.

Flights by other airlines were operating as scheduled at Cairo airport, according to the sources.

In response to British Airways' cancellations, the Egyptian Ministry of Civil Aviation said it had increased the seat capacity of national carrier EgyptAir's flights to London.

The ministry added it would operate an additional flight to Heathrow from Sunday during the suspension period.

The flight suspension has raised concerns in Egypt over potential harm to the country's vital tourism industry, which was recently showing signs of recovery after a years-long slump.

A senior Egyptian aviation official defended security at the country's airports.

"All Egyptian airports are well-secured. Security at them exceeds the standard rules," the head of Egypt's Civil Aviation Authority, Sameh al-Hefnawi, said late on Saturday.

He claimed the cancellations were politically motivated.

"The issue has nothing to do with aviation. It is political," he told MBC Masr, an affiliate of the Saudi-owned television network MBC.

"Whenever Egypt is recovering, a fabricated crisis happens," al-Hefnawi added.

In its updated travel warning for Egypt, the British Foreign Office refers to British Airways' decision and points to an increased terrorism risk for air traffic.

The Foreign Office warns against non-essential travel to Sharm el-Sheikh, where in 2015 a bomb exploded on a Russian passenger jet shortly after take-off, killing all 224 people on board.

The bombing, which was claimed by the Islamic State terrorist organisation, prompted multiple countries to cancel flights to the Red Sea resort town.

Egypt has seen a spate of militant attacks mainly targeting security forces and minority Christians since the army's 2013 overthrow of democratically elected but divisive Islamist president Mohammed Morsi.

Tourism, a main source of national income, has in recent months shown signs of recovery after having been hit hard by the unrest that followed Egypt's 2011 uprising and post-Morsi turmoil.

This week, unknown gunmen carried out several deadly attacks, including a suicide bombing, in the province of North Sinai, a hotbed of violent militants.

Islamic State claimed the suicide attack.

Australian Associated Press