The 39-year-old actress was flying from Detroit to Los Angeles when she noticed a uniformed U.S. serviceman at her gate. She discreetly asked to switch seats with the man, and gave up her first class seat to sit in coach.
"I noticed Ms. Adams was in first class and as I was getting seated, I saw the flight attendant guide the soldier to Ms. Adams' seat," passenger Jemele Hill tells ABC News. "She was no longer in it, but it was pretty clear she'd given up her seat for him. I was incredibly impressed, and I'm not even sure if the soldier knew who gave him that seat. I guess he will now!"
The actress, whose father was in the U.S. military, spoke to the soldier in private before she returned to her new seat in coach.
"Ms. Adams did it so quietly and quickly that it speaks to her character," Hill lauds. "And somebody in coach just got a helluva seat mate!"
Adams will appear in new Tim Burton film Big Eyes later this year.
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