Yes you can bring snacks onto the plane in reasonable quantities in your carry on luggage or in your checked luggage.
I've flown several times and bring my own snacks such as crackers, chips, granola bars etc and it's never been a problem.
You can also bring baby formula and other baby stuff on the plane that you need to care for your baby if you have one.
Yes you can take and bring baby formula on a plane.
When you're flying with a baby that needs formula you can bring formula onto the plane to feed the baby.
Formula can be brought onto the plane either in in liquid form or powder form and you can also bring frozen water onto the plane so that you can make a bottle of formula on the flight.
You can bring breast milk, baby food, baby food pouches, teething rings etc onto the plane for your baby.
According to the TSA rules baby formula, breast milk or juice in quantities greater than 3.4 ounces or 100 milliliters are allowed in your carry on luggage.
Other things allowed in carry on luggage on the plane are liquid-filled teethers, canned, jarred and processed baby foods.
The airlines know that you need to feed your baby and care for them so they do allow baby formula on the plane and even baby wipes.