UEAir United Eagle Airlines, Chengdu, China, 2004-2010,
2010 Renamed to Chengdu Airlines(q.v.).             - #2:

Ukraine International, Kiev, founded 1992.
  glossy paper  #2,    #4,    #8,         normal paper #9(sealed base)/#10(flat base):

UNI AIR, Taoyuan, Taiwan, founded 1998:   
    -                    #2,                                                              #4:    

   -                  #10,                                                     #1:

UN Interim Forces, Beirut, Lebanon.     -  #1:

United Airlines, Chicago, USA, founded 1929.
  -  #6,                                  #4/#9(smaller bag, bold print),                     #1:     

-        #2/#3/#19 (diff base):

United Airways BD, Dhaka, Bangladesh, 2005-2014.   -   #1,                     #2:

Urumqi Air, Urumqi, Xinjiang Province, China, founded 2014.    -   #1(front and rear shown):

US AIR, Tempe, Arizona, USA, founded 1979 by renaming from Allegheny Airways,
1996 renamed as US Airways -   
#1,                                                                      #1a:    

#2/#4(diff. cut),                                                  #6:

US Airways,  - #1:

US Air Force, Washington, USA.  Generic white plastic bag in brownish envelope.  - #2:

US-Bangla Airlines, Dhaka, Bangladesh, founded 2014.   #1:

UTA,  France, 1963-1990.           -  #3(pointed base),   #9(flat base):

Uzbekistan Airways, Tashkent, founded 1992.  -  #1/#2(brighter colors, bold letters),    #5,       #8:

      -       #9  (front and rear):