Unaccompanied Minors

Because United almost didn't let me on the plane because I didn't look old enough, I decided to look up age restrictions for popular airlines.

American Airlines:

0-5 Children under 5 years of age may not travel alone under any circumstances.
5-7 Can only travel on nonstop or direct flights. They can’t travel on certain flights on smaller aircraft when a flight attendant is not required.
8-14 Can travel on any nonstop or direct flight, or any connecting flight through Charlotte, NC (CLT), Washington Reagan, D.C. (DCA), Dallas Forth Worth, TX (DFW), New York, NY (JFK and LGA), Los Angeles, CA (LAX), Miami, FL (MIA), Chicago, IL (ORD), Philadelphia, PA (PHL) and Phoenix, AZ (PHX).
15-17 Children in this age range don’t have to use the unaccompanied minor service, but it’s still available to them. When traveling alone, children 16 years of age and older can book online, to book children 15 years of age, you’ll need to call Reservations.

Children 2-14 years old can travel as an 'accompanied minor' with someone 16 years or older

You have to be 15 years old to sit in the emergency exit row.

Southwest Airlines:

Children ages 5 through 11 traveling without an accompanying Passenger age 12 or older must travel as an Unaccompanied Minor (UM) on Southwest Airlines.

Children ages 12 through 17 traveling without an accompanying Passenger age 18 or older are considered Young Travelers (YT) on Southwest Airlines.

You have to be 15 years old to sit in the emergency exit row.

Delta:

4 years of age and younger: Not permitted to travel alone. Must be accompanied by a passenger at least 18 years of age.

Delta provides special services for children who are flying by themselves. Children 5-14 years of age traveling without an adult (18 years plus) are considered an Unaccompanied Minor (UMNR) and must participate in the UMNR program.

Unaccompanied Minor (UMNR) service is mandatory for ages 5-14. Children ages 15-17 are not required to have unaccompanied service; however, we will provide the service if requested. The UMNR service fee will apply.

You have to be 15 years old to sit in the emergency exit row.

United:

Children younger than 5 years of age are not accepted as unaccompanied minors.

Children 5 to 15 years of age who are traveling alone must use our unaccompanied minor service. A service charge will apply.

Unaccompanied minor service is not available for children over age 15. Children ages 16 and 17 may travel alone on any United- or United Express-operated flights.

You have to be 15 years old to sit in the emergency exit row.

Overall, most sites suggest similar age restrictions. They all have the same age limit for sitting in an emergency exit row, which means the staff in charge of boarding my plane thought I could be younger than 15.