A lot of things go into facilitating a smooth air travel experience—like gathering your necessary documents, packing within appropriate weight limits, and beating traffic (and those insanely long security lines) to make it in time for your flight. But just as crucial as knowing what to do is what not to do so that you arrive at your destination feeling fab (instead of foggy) and rested (instead of reeling). As such, there are a few foods and drinks you may want to avoid as you take to the skies, and few people would know better about what those are than a pilot.

Ahead, find out which foods and drinks to avoid in-flight, according to Paul Janowicz, First Officer, A320, for Delta Airlines.

1. Alcohol

It might be tempting to order a hard drink when the bar cart strolls your way, particularly if you want to take the edge off as a nervous flier or kick off your vacation with a bit of bubbly. As nice as the first sip or two might feel in the moment, it’s likely to do more harm than good by the time you land.

“Alcohol can dehydrate you and make you feel groggy and tired after the flight,” says Janowicz. “Due to the pressure changes in the cabin, a person will get intoxicated faster drinking in-flight than on the ground.” In other words, chances are even a single Bloody Mary or glass of wine will make you feel hungover once you’re back on land.

2. Coffee

I take my caffeinating seriously, and it truly pains me to tell anyone to lay off the java—even more so if you’re out of sorts from an early wake-up or want to hack your biological clock to adapt more quickly to your destination’s time zone. However, Janowicz warns that coffee is one of the top foods and drinks to avoid in-flight.

“While it may be nice for those early morning flights, the caffeine in coffee will dehydrate you in an already dehydrating cabin environment,” he warns. Plus, food safety experts and flight crews alike are privy to a dirty little secret: The tank water used for airplane coffee (and tea) isn’t the cleanest, to say the least—so you’ll be doing yourself a favor in several ways by passing on a brew.

3. Carbonated drinks

You’re better off limiting sugary sodas for the sake of your health as a general rule. But other carbonated drinks, including diet soda and seltzer, also nail a spot on Janowicz’s no-fly list. “The carbonation can cause gas and bloating, especially if drinking while the plane is climbing or descending with the pressure changes that occur in the cabin,” he warns.

Those who already struggle with digestive distress may want to take extra care to limit these bubbly bevs on the day of travel. However, every flier would be all the wiser to sip on plain bottled H2O before, during, and after the flight—even if that warrants a few extra trips to the tight airplane lavatory.

4. Spicy foods

I love spicy foods just about as much as I love coffee, going as far to pack both cold brew packets and a bottle or two of hot sauce when I travel. But according to Janowicz, I’m better off keeping both in my checked luggage instead of having them accessible in my carry-on. “Generally our menus onboard are very mild, but I would not pack any snacks that might have spice involved as it may cause stomach discomfort in-flight,” he shares. It’s also smart to avoid a spicy meal before takeoff—whether at home or at an airport restaurant—if you want to reduce the risk of experiencing fiery digestion en route.

5. Fried foods

Fried foods are another category you’ll want to steer clear of on the day of flying (as well as limit in your daily diet for the sake of your heart health¹, mental health², and overall well-being). “Eating something fried before or during a flight usually has higher sodium involved, which dehydrates the body and can also cause symptoms like gas and bloating,” Janowicz explains.

Instead, aim to pack and fill up on nutritious fare that’s as fresh as possible, and enjoy your packaged in-flight freebies in moderation. Janowicz says Delta offers lightly salted almonds, which offer a decent amount of plant protein, healthy fats, and fiber—plus a majorly satisfying crunch.