Greece has vowed to shoot down any aircraft trying to wreck the Olympics with a 11 September-style attack.
Nato Awacs will patrol Greek skies
Any such plane "won't reach its target," Public Order Minister Giorgos Voulgarakis told state television.
However, the minister said such action would only be taken if a plane refused to change course after being warned.
Nato Awacs surveillance planes are also to boost the massive security effort planned for the games, which are taking place in Athens 13-29 August.
It is feared the huge profile of the Olympics - the first summer Games to be held since the attacks on New York, Washington, Bali and Madrid - could make Athens a prime target for terrorists.
"If a renegade plane, a plane that is not on its proper course over Greece, enters restricted airspace, and does not change course after being warned, it will not reach the Olympic stadium," Mr Voulgarakis said.
Greek special forces have staged a series of security exercises
He was speaking after organisers unveiled their plans at a three-day security briefing for representatives of the 202 nations participating in the Olympics.
About 70,000 police officers and soldiers will be patrolling the "Olympic village" northwest of the Greek capital and also all the Olympic venues.
In addition, tough restrictions on the movement of vessels in the Saronic Gulf off Athens will be in place.
The International Olympic Committee earlier this month highly praised Greece's $1bn security arrangements for the Games - nearly four times what was spent in Sydney in 2000.
On Wednesday, US and Australian Olympic Committees - which in the past have questioned security arrangements - also said they were impressed by the security preparations.
"Greece will organise the safest Games that can be organised," US Olympic chief security officer Larry Buendorf said after attending the security briefing in Athens.