Israeli authorities plan to issue a new anti-hijack identification system to incoming aircraft which they say is foolproof, but some experts are not convinced it will plug all the security holes on the horizon.

Starting next year, Israel will require pilots who fly to its airports to use the Security Code System (SCS), a local invention designed to ensure planes that have been commandeered for Al-Qaida-style attacks are spotted in time.

Israel plans a trial run for the system, using a credit card-sized keypad, next month, in cooperation with five airlines from the United States, Europe and Africa. About 10,000 of the units will ultimately be issued, with Israel bearing the cost.

Pilots who fail the authentication test when they approach Israeli airspace will be denied entry. Should a plane go ahead, ignoring further warnings, Israel will consider it hostile and scramble fighter planes for an interception.

In the worst case, that could mean an aircraft is shot down.

"You can't bluff this system," said Dani Shenar, chief of security for Israel's Transportation Ministry.

"It provides a higher level of confidence that the aircraft is being controlled by the right people, which is a huge asset in terms of avoiding unnecessary security alerts."

He said the system knows how to differentiate between "a classic hostage-taking hijacking and a 9/11-style hijacking".

Omer Laviv, an aviation security expert with the Israeli company Athena GS3, said some pilots may be reluctant to signal their predicament.

"That would mean certain death, while if you give the correct code, perhaps the attacker would be willing to land and to negotiate. Now, this is a big dilemma," Laviv said.