IAG International Airlines Group,  registered in Madrid, Spain,  and headquartered operational in London, UK, was founded in 2011 by merger of  British Airways and Iberia. Bag #1 was branded British Airways Iberia,
in 2015  a bag with rear instructions in now 9 languages and  new name was launched - #2(front and rear):

Iberia, Madrid, Spain, founded 1927.      # 8 and    #2:

                                              #5         and                #17:

    -  #1/#13/#24,                    #20,                           #25,                     #27/#21upside down print:

Air Nostrum, Valencia, Spain, founded 1994. Operating exlusively for Iberia regional.
         # 5,  further q.v. Air Nostrum

Iberworld, Palma de M., Spain,  1998 - 2011renamed as Orbest Orizonia (q.v.)     
-                     #1,                              #3,                                                 #9:

-     #5,                                                          #6:

Ibex Airlines, Koto, Tokyo, Japan, founded 2000.    -     #1:

ICARO Air, Quito, Ecuador, 1971-2011.     -   #3,        #6(30cm tall),              #7:
                                            
Icelandair, Keflavik, founded 1979 by merger of Loftleidir(q.v.) and Flugfelag.    
-               #1,                                      #2glossy/#4normalpaper,                            #7:

-                         #8,                                             #10,                                       #3:

-                        #13,                                           #14:

INDIAN Airlines, New-Delhi, India, founded 1953.
-      #11,                                   #13,                   #5/#2(smaller types, diff maker):

#22(front and right gusset):

IndiGo, Gurgaon, Haryana, India, founded 2005.      - # 4,          #6/#7/#8(diff maker in gusset):

Indochina Airlines, Ho Chi Minh City, 2008-2009.  - #1:

Indonesia Air Asia, Jakarta, founded 2004 by renaming from Awair(Air Wagon Int´l.).
-  #2(flat base)/#4(pointed base),                               -   #5:

Inex Adria Aviopromet, Ljubljana, Yugoslavia, 1968-1986.
Renamed to Adria Airways(q.v.) on Slovenia split off Rep.of Yugoslavia.  -#1:

Inter European Airways, Cardiff, Wales, UK, 1987-1994, merged into Tomas Cook. - # 2:

Interflug, GDR, 1958-1991.    -    #1,                 #2,                   #3,                          #6:

Interisland Airlines, Pasay City, Philippines, founded 2004 by renaming from Interisland AirService. - #1:

InterSky, Bregenz, Austria,  2001 - 2015.      -  #1       and        #2(front and rear):

# 3:

Iran Air, Tehran, founded 1962.   #6 and  #4, #10 and 10a (types different sizes):

-                #8,                                     #1,                              #5,                                       #2:                 

-     #14/#14a(lighter colors):

Iran Airtour, Tehran, Iran, founded 1973.   -     #2,                  #3:

Iran ASEMAN Airlines, Tehran, founded 1980.
      -       #1/#1a(blue clip),                  #8,                            #10,                             #9:

       -           #11,                                                 #12:

Iraqi Airways, Bagdad, 1945 - May 2010.   -  #7,            #4,           #1,                #8a:

Island Air, Honolulu, Hawaii, USA, founded 1980 as Princeville Air, renamed 1995 to Island Air. - #2:

Island Aviation Inc, Pasay City, Philippines, founded 2003 by renaming from A.Soriano Aviation (q.v.).
-    with thanks to Gerd Clemens -  #1:

Island Aviation Services, Male, Maldives, 2000 - 2008 renamed as Maldivian(q.v.).    -#1:

Island Transvovager Inc.(ITI), Pasay City, Philippines, 2002-2015 renamed to Air Swift.   -  #1:

ISRAIR, Tel Aviv, Israel, founded 1989 as Knafei HaEmek (Valley Wings),
renamed 1996 to Israir Airlines.     -    #1,                  #4,                            #2:

Istanbul Airlines, Turkey, 1985-2000        #1

ITA Airways - Italia Trasporto Aereo, Rome, founded 2020.  -  #1:

Itapimirim Transportes Aereos, Rio de J., Brazil, 1990 - 2000.