(CNN) — Much of Boston's transportation system followed the rest of the city into lockdown mode Friday as authorities hunted for one of the suspects in this week's deadly marathon bombings.
All modes of transit operated by the Massachusetts Bay Transportation Authority -- including rail, subway, buses and ferries -- were halted Friday at the request of the police, according to Joe Pesaturo, an MBTA spokesman. The Massachusetts Department of Transportation cautioned travelers via Twitter not to wait at stations or bus stops.
Boston's Logan International Airport was operating normally under heightened security, according to airport spokesman Matthew Brelis.
"It's open and operating and flights are operating," he said. "Airlines are waiving fees for passengers who don't want to or can't fly today. ... Taxis are coming and going. Call your airline for your flight status before you leave for the airport, which is what we say anyway, but allow yourself a little extra time."
Taxi service in the city of Boston was suspended Friday morning but was restored by about 11 a.m., according to the Boston Police Department's Twitter feed.
Traveler Karen Lo arrived Friday at Logan on a flight from Canada to attend a biology conference at the Boston Convention & Exhibition Center. Lo said she wouldn't have noticed anything particularly unusual if she hadn't been following the news online. But after talking to airport information officers, she decided to go to her colleagues' hotel near the airport rather than trying to check into her room in the city center.
"I thought it would be safer for me to stay with people that I knew before I ventured out into the city by myself," Lo said.
The conference she's attending is scheduled to start Saturday, and Lo said she hopes to make it to her hotel later. Right now, she's in wait-and-see mode.
The city's convention organization is providing regular updates to attendees and organizers of meetings scheduled over the weekend. A statement Friday afternoon advised attendees who were not already heading to facilities to hold off until further information is available.
Many airlines were waiving fees for Boston travelers.
JetBlue Airlines allowed travelers with Friday flights to or from Boston to change them without incurring fees or fare differences for travel through Monday. Passengers with canceled flights may also opt for a refund, the airline said on its website.
Delta Air Lines was allowing Boston travelers to change plans "due to heightened security in Boston affecting ground transportation to Logan Airport," the airline said on its website. Delta will waive ticket change fees one time for travel scheduled between Friday and Sunday going to, from or through Boston. Fare differences may apply for itinerary changes where rescheduled travel occurs after Wednesday.
Flight operations at Logan appeared normal Friday morning, according to flight tracking site FlightAware.
"Flights at Boston Logan are operating normally and are nominally on-time this morning with no increase in cancellations over a normal day," according to FlightAware CEO Daniel Baker.
The Federal Aviation Administration ordered a 3.5-nautical-mile temporary flight restriction over Boston "to provide a safe environment for law enforcement activities." The restriction is from surface to 3,000 feet, according to the FAA.
Amtrak has suspended service between Boston and New York. Earlier it had suspended service between Boston and Providence, Rhode Island.
"At the request of local authorities, and due to ongoing police activity, Amtrak Acela Express and Northeast Regional service remains suspended indefinitely in the Boston area. Northeast Corridor trains are terminating at New York Penn Station," Amtrak said in a statement.
The railroad's Downeaster service continues to operate a modified schedule with no service to Boston. Operations are normal between Washington, Philadelphia and New York.
An Acela train coming from Boston was searched and "cleared" near Norwalk, Connecticut, on Friday morning, according to Amtrak spokesman Cliff Cole. The incident was related to the Boston Marathon investigation. After the search, the train proceeded to Washington's Union Station.
Greyhound and BoltBus operations in and out of Boston have been canceled until further notice, according to spokesman Timothy Stokes.