Last month, SpaceX founder Elon Musk laid out a bold plan to colonize Mars. He believes the first humans will step on the red planet as soon as 2025. It turns out Musk could face some tough competition from Boeing, which recently claimed it would be the first company to successfully send an astronaut to Mars.

Speaking at a tech summit this week, Boeing CEO Dennis Muilenburg took an indirect shot at the rival upstart aerospace firm. “I’m convinced that the first person to step foot on Mars will arrive there riding on a Boeing rocket,” he said.

Boeing’s plans to send humans to Mars hinge on the Space Launch System rocket, which is still in development with NASA. According to Ars Technica, it could cost another $60 billion before the SLS is ready. That means Boeing’s rocket likely won’t bring anyone to Mars until at least the late 2030s.

Muilenburg seems to be implying that Musk won’t meet his ambitious timeline, which plenty of critics agree with. or that Boeing plans to significantly accelerate its schedule to beat SpaceX to the punch.

You can watch the full interview, which also touches on Boeing’s plans for supersonic, hypersonic and low-earth orbit space travel, embedded below.