CAIRO, Feb 25 (Reuters) - Egypt expressed frustration on Saturday at Britain's refusal to lift a suspension of flights from the United Kingdom to the Red Sea resort of Sharm al-Sheikh, imposed after Islamic State brought down a Russian airliner in 2015.

The issue of airline security came up in talks involving visiting British Foreign Minister Boris Johnson, Egypt's President Abdel Fattah al-Sisi and Foreign Minister Sameh Hassan Shoukry.

Johnson praised Egypt as a longstanding friend of Britain and said they were strong allies against terrorism and extremist ideas, according to a British statement.

But Shoukry said Britain's continued suspension of flights to Sharm al-Sheikh, once a popular destination for British holidaymakers, was unjustified.

Britain and Germany both imposed bans on flights to certain places in Egypt following the downing of the Russian airliner over the Sinai Peninsula in which all 224 people on board were killed. Russia suspended all flights to Egypt and has yet to restore them.

"The continuation of the halt of the British airline to the Egyptian tourist destinations despite the progress that has been made in securing airports is completely not understandable and unjustified," an Egyptian foreign ministry statement said.

More than six years of political turmoil in Egypt since the overthrow of Hosni Mubarak in 2011 have scared off investors and tourists.

The flight suspension was hitting Egypt's economy hard and was "inconsistent with Britain's repeated promises to support Egypt", the statement said.

The British statement did not mention when flights would resume.

During Johnson's visit, Britain and Egypt completed a $150 million loan guarantee agreement to help Egypt complete its programme of economic reforms, the British embassy said.

(Reporting by Amina Ismail and Mostafa Hashim) ((amina.ismail@thomsonreuters.com; +20 2 2394 8114;))