NASA officials still have not provided Congress a plan or budget proposal that would allow for a return to the moon four years early -- even though the Trump administration directed the agency to do so in March.

Congressional leaders are getting anxious.

"We're flying blind," U.S. Rep. Kendra Horn, an Oklahoma Democrat, said during a hearing of a subcommittee of the U.S. House Committee on Science, Space and Technology. "The lack of planning evident so far is no way to run a human exploration program."

She added that the new target date "left NASA scrambling to develop a plan and hastening to pull together a budget amendment that still hasn't been delivered."

But the answer from NASA still is the same: The proposal isn't ready. And it won't be for "several weeks," said Bill Gerstenmaier, the agency's associate administrator for human exploration and operations.

"We recognize this is a challenge and we need a really solid plan," he said.

Though no official plan has been released, NASA Administrator Jim Bridenstine has shared details in recent weeks about how he thinks the agency would get to the moon four years early.

The plan would include help from international and commercial partners, as well as the use of a mini-space station that NASA wants to build orbiting the moon and the agency's Orion spacecraft-Space Launch System rocket duo.

Agency officials say the rocket is vital for the moon 2024 plan, but it has experienced significant delays since Boeing started building it in 2012.

Last week, Gerstenmaier admitted that it likely wouldn't be ready for a launch without humans around the the moon until 2021, even though NASA had been hoping it would happen in 2020.

Still, Gerstenmaier said he believes a 2024 human lunar landing is doable -- assuming the agency get the necessary support.

"The question is, can we get through the political process? Can we get the funding?" he asked.

That will depend on the reason for the accelerated timeline, said U.S. Rep. Eddie Bernice Johnson, from Texas -- and it needs to be a good one.

"NASA has provided no specifics," Johnson said. "I hope that when NASA delivers a plan, it will also provide a compelling rationale for this proposed crash program."

Alex Stuckey writes about NASA and science for the Houston Chronicle. You can reach her at alex.stuckey@chron.com or Twitter.com/alexdstuckey.