WASHINGTON, Oct 19 (Reuters) - A group of 11 states and the District of Columbia on Monday urged the U.S. Environmental Protection Agency (EPA) to strengthen the first-ever proposed standards regulating greenhouse gas emissions from airplanes and other aircraft.

The state attorneys general led by California said the EPA emissions rules proposed in July were "entirely insufficient."

California Attorney General Xavier Becerra said the "sham proposal to regulate it is the equivalent of doing nothing."

The EPA said in July the proposed requirements would apply to new-type designs as of January 2020 and to in-production airplanes or those with amended type certificates starting in 2028. The EPA did not immediately comment Monday.

The state attorneys general joining the letter include Connecticut, Illinois, Maryland, Minnesota, New Jersey, New York, Oregon, Vermont, Washington and Massachusetts.

"The EPA can and must adopt effective standards to substantially reduce these emissions, mitigate existing climate harms, and avoid the worst economic and public health outcomes of an unmitigated climate crisis," the states said.

In 2016, the U.N. International Civil Aviation Organization (ICAO) agreed on global airplane emissions standards aimed at makers of small and large planes, including Airbus SE and Boeing Co, which both have backed the standards.

The EPA-proposed regulation seeks to align the United States with the ICAO standards, EPA Administrator Andrew Wheeler said in July.

The 11 states said the EPA proposal would "lag existing technology by more than 10 years and would result in no GHG reductions at all compared to business-as-usual." Boeing declined to comment.

Aircraft account for 12% of all U.S. transportation greenhouse gas emissions and 3% of total U.S. emissions. They are the largest source of transportation greenhouse gas emissions not subject to rules.

Wheeler said in July the proposal is based on "where the technology is today ... You can't really set the standard that can't be met."

Under former President Barack Obama, the EPA in 2016 declared aircraft emissions posed a public health danger. (Reporting by David Shepardson Editing by Chris Reese and Marguerita Choy)