I flew business class for the first time and was surprised that my casual go-to outfit made me so uncomfortable

• I flew business class for the first time this year and made one mistake: dressing too casually.
• While business attire isn't required on JetBlue, I noticed I was the only passenger in cozy clothes.

As I approached the gate for JetBlue's inaugural flight to Paris last month, I felt my heart sink a little deeper into my chest.

I'd been looking forward to the flight for weeks, so it wasn't nerves about the travel or anxiety about the reporting trip I'd soon be embarking on. Instead, it was because within a matter of seconds, I realized I was the odd man out.

I looked down at my beat-up New Balance tennis shoes, wide-leg Old Navy yoga pants, and tank top, then back up at the crowd that had gathered to board. In a sea of people who'd come to test out the new route in JetBlue's Mint business class, I was the only one who hadn't dressed up. Men wore slacks and button-up shirts, while women wore trousers and a blouse, a skirt, or a dress.

I'd been so busy planning what I'd wear once I landed that I hadn't even considered dressing up for the flight — and immediately wished I had gone business casual instead of my typical cozy airplane outfit.

From what I could tell, I was the only person wearing casual, comfy clothes

To give myself credit, my Old Navy pants can kind of be passed off as trousers if you don't look at them too closely. Plus, JetBlue doesn't have a stated dress code for passengers flying in its Mint business class, and no one commented on my outfit or requested that I change, so it's not like I violated an explicit rule.

My discomfort was more of a personal problem, a feeling like I was the only person to show up to a themed party without a costume. It was a feeling that I had committed a travel faux pas, that I had breached a law that everyone else implicitly understood.

While sitting at the gate, I slipped a sweater over my halter top and sent a frantic selfie to my coworkers asking for reassurance. They assured me I didn't look too much like a slob, and I put the idea to rest for the time being.

Still, I haven't stopped thinking about my fashion slip-up.

Next time, I would pick a business-casual — yet comfortable — outfit

In an interview with Who What Wear, the cabin crew described the kinds of outfits that help people get upgraded to first class. Employees said passengers should avoid "jeans, joggers and dirty trainers" — guilty.

"For an upgrade, it's all about looking the part. Smart but understated," one crew member told the outlet. "You should look like you travel often. But don't be dripping in designer clothing."

With that in mind, if I ever get to fly business class again, I'll plan to wear a more business-casual outfit: a pair of fitted trousers with a nice sweater or button-up shirt or a comfortable-but-upscale dress. I'd also ditch the tennis shoes for a pair of nice loafers or flats.

At the very least, I would choose a nicer top to go with my pseudo-trousers — and pack a nice pair of pajamas for an overnight trip.