WASHINGTON — Long a punch line for harried Northeast travelers, Amtrak has come to dominate commercial travel in the corridor connecting Washington, New York, and Boston, and this summer its trains are packed.
A decade ago, Delta and US Airways shuttles were the preferred mode of travel between the cities. But high fares, slow airport security, and frequent flight delays — along with Amtrak’s high-speed Acela trains, online ticketing, and workstation amenities — have eaten away at the airlines’ share of passengers.
Between New York and Washington, Amtrak said, 75 percent of travelers go by train, a huge share that has been building steadily since the Acela was introduced in 2000 and airport security was tightened after 2001. Before that, Amtrak had just more than a third of the business between New York and Washington.
In the same period, Amtrak said, its market share between New York and Boston grew to 54 percent from 20 percent.
Nationally, Amtrak ridership is at a record 30 million people; the Northeast accounts for more than a third of that and is virtually the only portion of Amtrak’s system that makes money.
“On the train, you’ve got power outlets and Wi-Fi, you can talk on the phone — it’s usable time,’’ said George Hamlin, an aviation writer and airline consultant who frequently rides Amtrak between Washington and New York. ‘‘Even I’m guilty of it,’’ he said of taking the train.
By 2040, given the trends, Amtrak said traffic in the corridor could reach 43.5 million passengers, almost four times the level today.
But success is taking a toll. Most days, trains in the Northeast are full. Several locomotives and railcars are 30 years old or more. Aging rails, bridges, and tunnels hold down top speeds and limit expansion of the network.
Last month Amtrak unveiled an ambitious $151 billion proposal to speed up trains and upgrade bridges and tracks.
But the plan is opposed by conservatives in Congress, who say the government-subsidized railroad has been a failure and should be privatized. Amtrak gets about $1.3 billion a year from the government but still loses money — $1.2 billion last year.
‘‘Money has always been an issue, and it will be,’’ said Joseph H. Boardman, president and chief executive of Amtrak. ‘‘But we realize we can’t stand still. We have a plan in place, and we have to keep moving forward.’’
Part of Amtrak’s success reflects the inconvenience of air travel, which does not easily allow travelers to work as they move.
Even if the air shuttles worked perfectly, there is still the cost and time of traveling to the airport, waiting at the gate, sitting on the taxiway, and finally getting into the air.
Amtrak’s fastest train makes the trip between Washington and New York in 2 hours 45 minutes, while planes travel the distance in 1 hour 20 minutes. Equivalent times for the New York-Boston trip are 3 hours 40 minutes for train, and 1 hour 15 minutes for plane. But transportation experts say adding in the ground travel and waiting times for air travel erases the difference.
On a recent trip to Boston from New York, Fernando Valdes, a management consultant, said airport security was a main reason he decided to take the train.
‘’It’s easier. I don’t have to take my shoes off,’’ he said as he shared a drink with a friend in the Acela cafe car.
Frequent flight delays, often caused by weather or congestion, have also played a role in the switch from planes to trains. Amtrak arrives on time 90 percent or more of the time, according to its data. Delta said the shuttle’s on-time percentage is ‘‘in the mid-80s,’’ and US Airways said its record was a little higher.
The Acela has played a big role in attracting passengers in the Northeast. The trains averaged about 80 percent full and earned an operating profit of more than $200 million last year on nearly $500 million in revenue.
But Acela tickets can be costly and wireless service spotty, and Amtrak just added a cancellation fee policy for all of its trains. Acela fares between New York and Washington range from an average of $145 for regular business class to $351 for first class; New York to Boston, $104 to $251; and Boston to Washington, $163 to $393.
Non-Acela train fares between New York and Washington average $49 to $153 for coach and $120 to $193 for business class; New York to Boston, $49 to $133 for coach and $104 to $168 for business; and Boston to Washington, $70 to $185 coach and $144 to $233 for business class.
At US Air, the lowest one-way coach rate between Washington and New York was $236 as of Wednesday, with the lowest first-class fare of $335, before taxes and fees. Between New York and Boston, the fares are $229 and $314, and Washington-Boston, $62 and $369. Corporate and other kinds of discounts can lower the prices.
To accommodate demand, Amtrak wants to add cars to each of the 20 Acela trains now in its schedules, increasing Acela capacity 40 percent, the railroad said, or about 124 seats per train.
Amtrak plans to add the new cars by 2015, and by 2020 increase the frequency of the trains between New York and Washington.