Britain's transportation secretary says the security concerns that have led to cancellations and delays of international flights during the past few days may continue to inconvenience travelers for some time ot come.

Transportation chief Alistair Darling says the problem will not be going away anytime soon.

Interviewed on British television, Mr. Darling said as long as the threat of terrorism exists, so too will measures aimed at countering it. "I fear that for many years to come, we are going to be living in an age where there is a heightened state of alert. Sometimes, it will be quite severe. At other times, perhaps, less so. But it does mean that we are going to have to get used to increased security at airports. From time to time, that will be noticeable. At other times, things will be going on behind the scenes," he said.

The transportation secretary refused to discuss press reports here that the government had received intelligence indicating that the al-Qaida extremist network was focusing specifically on the mid-day British Airways flight from London to Washington that was repeatedly canceled and delayed last week.

Mr. Darling said, based on his information, the cancellations and delays over the past four days have been justified. He also stressed that, while the grounding of aircraft will be seen again, it is only an option that will be implemented when it is deemed to be absolutely necessary. "A decision to cancel a flight is comparatively rare. And let us get it in perspective - thousands of flights took place yesterday, and will go today. But where we decide that we have to cancel a flight, the grounds are very clear in our minds, and we are justified in taking that [decision]. But it is a minority of flights," he said.

Ultimately, decisions to fly or not rest with the individual air carriers, but strong government recommendations are almost always complied with.