Also Wednesday, the NTSB said found no indications in train records of overdue maintenance despite earlier reports that the brakes on the train may have been behind schedule for a check-up. The train was last examined in late May.
"We do have an independent train system ... [but] let's not try and disperse the blame. Let's put it on the decision makers and the leaders," Fenty said on "Good Morning America."
Fenty said that while replacing or retrofitting the cars "to make them more crash resistant" would have been expensive, "lives are more important than finances."
Despite the two NTSB warnings, transit officials had refused an upgrade because it would be expensive and complicated.
"We have planned for the replacement of these railcars and are in pursuit of the funding to make that happen," Catoe said Thursday.
In 1996, a Metro train of the same series failed to stop and crashed into an unoccupied train in what the NTSB called "catastrophic failure." After the crash the NTSB recommended a comprehensive evaluation of the cars. In 2002, D.C. Metro declined to make any changes. A similar crash took place in 2004, and the NTSB reiterated its warnings.
"In 2006 [the NTSB] asked them to look at old cars," Hersman told "GMA." "They did not retrofit the cars to the standard the safety board was looking for."
Hersman emphasized that the NTSB's role was to make recommendations, and that it was up to local and federal authorities to decide whether to act based on those recommendations.
Train operator Jeanice McMillan, 42, was among those killed in Monday's crash. She was running the train that struck the one in front it stopped on the tracks.
Other victims of the accident ran the gamut from a young mother of two to a military officer.
The military officer killed in the crash was Major General David F. Wherley Jr., who died alongside his wife, Ann. Both were 62. Wherley, a career military man had recently retired as the head of the D.C. National Guard. It was his order that scrambled jets over Washington, D.C., Sept. 11, 2001.
"He was as fine a public servant, as dedicated to the United States of America as anyone I have ever met," Fenty said.
Also on the train was 40-year-old Ana Fernandez, killed while on her way to a nighttime cleaning job. She left behind six children.
Passenger Dennis Hawkins, a 64-year-old retired teacher, died while on his way to teach a Bible class.
And Lavonda King, just 23 years old, was killed as she took the train to pick up her two sons from daycare. Her mother said King had dreamed of a better life for her boys and had recently signed the paperwork to open up a beauty salon.
McMillan, who had been on the job for four months, was also a mother. The son she raised by herself had started college in the fall. Her family said she took pride in her work on the train and ironed her uniform nightly.
"She loved the train. She would talk about what she did at work, or how this works," said her brother, Vernand McMillan.
ABC News' Lee Ferran, Sarah Netter and Jay Shaylor contributed to this report.