Terrorists could still get a bomb aboard a commercial plane through cargo, which is virtually unscreened, the Air India inquiry heard yesterday.

Kathleen Sweet, a lawyer, author and retired U.S. air force lieutenant-colonel, said air freight, and the workers who load it, are "a huge gap" in aviation security.

She said the gap must be closed before another terrorist strike like the June 23, 1985, Air India bombing, which killed 329 people, occurs.

"We have to do it. There is just too much access to the cargo hold," testified Ms. Sweet, who heads a company called Risk Management Security Group. "My unfortunate theory is unless we get on this quickly, a plane's going to go down, it's going to be in the cargo hold and everybody's going to be fighting the next war." Very little has been done to secure cargo even though passenger-screening techniques have improved dramatically in recent years, said Ms. Sweet.

She told the inquiry that airlines and courier firms don't want to pay to screen freight.

But Singapore Air and Lufthansa screen all cargo and are "very profitable," Ms. Sweet told commissioner John Major.

She identified other weaknesses in airport security, including the simple task of cleaning planes.

"I flew in on Air Canada yesterday and the plane was filthy, just filthy," Ms. Sweet said as Mr. Major smiled. "The fact that the garbage was piled up so significantly between the seats that something could be hidden in there." Trash could be hiding knives or liquid explosives that could be used in a terrorist attack.

"You better clean that airplane and make sure that anything that could be dangerous is removed. Check the toilets, for heavens' sake. Check the overhead bins. You have to do the whole thing. You can't just run a sweeper down the main aisle and say 'oh, the airplane is clean.' That's silly. That is dangerous." Aviation security expert Rodney Wallis also testified yesterday about the garbage problem, noting that a Korean Airlines plane was blown up in 1987 when terrorists left liquid explosives in a liquor bottle from the duty free store on board.

Mr. Wallis, who has testified extensively since the inquiry began looking at security issues last week, said he agreed with much of what Ms. Sweet said.

Both are opposed to armed air marshals because of the danger posed by guns on planes. Both said "no-fly lists" like the one Canada is implementing June 16 are ineffective.

Both said cargo security must be improved and there are often low-tech, cost-effective solutions to improving security that are not used.

Ms. Sweet said explosive-sniffing dogs could be used to check cargo. She also agreed with testimony from Senator Colin Kenny last week that all workers with access to planes should be screened.

Cargo could be tampered with at the factory where the product is manufactured, Ms. Sweet said.

Shippers such as DHL or Federal Express can drive right up to planes across North America, she added.

Mr. Wallis completed his testimony by saying that even in 1985, the series of events that led to a bomb-laden suitcase from Vancouver getting on Air India Flight 182 out of Toronto should have raised "red flags."