WASHINGTON — An Obama administration proposal that would have required airlines disclose checked and carry-on bag fees at the start of a ticket purchase rather than later is being dropped by the Department of Transportation. The department said in a notice posted online Thursday that it is withdrawing the proposed rule, along with a second, early-stage rulemaking to force airlines to disclose more information about their revenue from fees charged for extra services, because the rules would have been “of limited public benefit.” It also said airlines would incur “significant costs” if required to report their revenue from fees for services like early boarding or extra legroom. Work on the proposals was frozen shortly after President Donald Trump took office. Airlines are already required to disclose bag fees, but critics say the information is often hidden until after consumers have taken several steps toward purchasing a ticket and isn’t always clear.