A Marine Corps vet’s effort to highlight the crisis of soldiers dying by suicide nearly got her booted from a Delta flight … and she was forced to change her clothing before take-off.

Catherine Banks, who served 22 years in the Marines, says she was on a Delta flight in San Francisco earlier this week, when she says a flight attendant walked up to her and said, “You need to get off the plane.”

She says he told her the shirt she was wearing was “threatening.” The t-shirt had a print that read, “Do Not Give in to the War Within … End Veteran Suicide.”

Catherine told KNTV she was dumbfounded, and simply responded, “Are you kidding me?”

She says she explained she’d been in the service for over 2 decades, and was on her way to see her sister, who’s also in the Marines — but she claims the attendant said, “I don’t care about your service” … and told her she couldn’t get back on the plane until she removed the shirt.

Banks says she was filled with anxiety as she stood on the jetway bridge, and — after asking the flight attendant to turn around — she took off the shirt and replaced it with a sweatshirt.

She was finally allowed to get back on the plane, but the flight had now been delayed and Catherine says she missed a connection.

As for what was so threatening about her shirt — we’ve reached out to Delta, but no word back yet.

The data on military suicides are staggering — reportedly 22 veterans die by suicide each day, and the rate across all branches of the armed forces is 32 percent.

We’ve reached out to Delta for comment … so far, no word back.