The major airlines, already struggling before the attacks that grounded them for two days, have battled to rebound with flights operating on reduced schedules and many planes flying at less than half capacity.
"Unless we rebuild confidence among the American people in the safety of the skies, the impact on air commerce will be worse and will affect other sectors of the economy," Senator Joseph Lieberman, a Connecticut Democrat, said at a hearing.
That plan would improve the strength of cockpit doors and expand the federal air marshals program. Air marshals are armed, plain clothes federal agents who ride on domestic flights.
In other developments, Defence Secretary Donald Rumsfeld said Washington will not launch a massive D-Day invasion to win its campaign against terrorism, but is preparing instead for a long fight.
"The truth is this is not about revenge. It's not about retaliation. This is about self defence," Rumsfeld said. "The United States of America knows that the only way we can defend against terrorism is by taking the fight to the terrorists."
Bush has built a formidable coalition behind his "war against terrorism," succeeding in virtually isolating Afghanistan's Taleban rulers. Saudi Arabia has announced it had cut ties with the Taleban, leaving Pakistan as the only country which still has diplomatic relations with Kabul.
For the first time in its history, the Taleban face enemies wherever they look. Russia, China, Iran, and India all want the Taleban hard-liners out. With the overt approval of Moscow, the former Soviet Republics of Kazakhstan, Tajikistan, Uzbekistan and Turkmenistan are also cooperating with the United States.
Russia hinted has hinted that its ally Tajikistan might offer US forces the use of Dushanbe airport for possible attacks on Afghanistan.
Taleban leader Mullah Mohammad Omar, in a message faxed to Reuters, appealed to Americans to "use your sense" rather than blindly follow their government's policy to attack his country.
"You should know whatever incidents and sorrow you suffer ... are a result of the erroneous policies of your government," he said.
- REUTERS
Map: Opposing forces in the war against terror
Afghanistan facts and links
Full coverage: Terror in America