Yes, you can wear leggings on United (but airline can police your clothing).

Outrage, Explanations After United Turns Away Girls From Flight For Wearing Leggings : The Two-Way : NPR

United Airlines: leggings ban 'not sexist' even though it affects women more, US news

United Airlines: 'Your leggings are welcome' — as long as you're paying for your flight - The Washington Post

United Airlines Says Women May Be Denied Boarding for Wearing Leggings - View from the Wing

Can guys wear leggings like girls? - Quora

Johnston's new school dress code is called 'sexist' and body shaming to female students

Outrage, Explanations After United Turns Away Girls From Flight For Wearing Leggings : The Two-Way : NPR

Can I Wear Leggings On A Flight To Nyc

Can I Wear Leggings On A Flight To Nyc

United Airlines caught up in leggings row - BBC News

Can You Wear Leggings On A Plane? – solowomen

Outrage, Explanations After United Turns Away Girls From Flight For Wearing Leggings : The Two-Way : NPR

United Airlines Refused to Let Passengers on Board Wearing Leggings

Can you wear leggings and joggers on an airplane? - Quora