First, note that the US government allows airlines to board you for travel to the US with an expired 10-year green card, without needing a transportation letter or anything else. See the CBP carrier information guide, page 28:Cards with expired I-551s may be boarded without penalty if the card was issued with a 10-year expiration date.However, I am not sure if there are any airlines that are willing to board you with an expired green card, even though they are allowed to. If the airline refuses to board you, and you have been abroad for less than 1 year, you can file form I-131A with a US consulate to apply for a u201ctransportation letteru201d that allows the airline to board you. On the u201cSpecial Instructionsu201d section on that web page, it confirms that a transportation letter is not necessary for an expired 10-year green card, but if the airline wonu2019t board you, you might need one anyway:If you have an expired Green Card, you may not need to file Form I-131A. Although regulations generally require an LPR to travel with a valid Green Card, U.S. Customs and Border Protection (CBP) policy permits a transportation carrier bound for the United States to allow you to board without carrier documentation if you:Are an LPR with an expired Green Card that was issued with a 10-year expiration date (and you have been outside of the U.S. for less than a year);[u2026]Check with your airline or transportation carrier before you file Form I-131A because, in some situations, the airline or transportation carrier may still refuse to let you board even if you are in one of the categories above. In that case, you will need to file a Form I-131A.If you have been outside the US for more than 1 year, the consulate will not issue you a transportation letter, and will insist on you applying for an SB-1 returning resident visa, which requires you to prove that you couldnu2019t return earlier due to circumstances beyond your control, which is very hard.Or, if you can somehow make it to a US land border port of entry, you can try to enter, and the officer has discretion to let you in anyway even if you have been outside for more than a year, if he/she determines that you have not abandoned residence. Or, if he/she refuses to let you in, and you refuse to voluntarily give up your permanent residency, he/she will place you in removal proceedings in immigration court, and the immigration judge can let you in as a permanent resident if he/she determines that you have not abandoned residence.