ABC News has obtained an internal State Department email from May 3, 2012, indicating that the State Department denied a request from the security team at the Embassy of Libya to retain a DC-3 airplane in the country to better conduct their duties.

Copied on the email was U.S. Ambassador Chris Stevens, who was killed in a terrorist attack on the diplomatic post in Benghazi, Libya, Sept. 11, 2012, along with three other Americans. That attack has prompted questions about whether the diplomatic personnel in that country were provided with adequate security support.

No one has yet to argue that the DC-3 would have definitively made a difference for the four Americans killed that night. The security team in question, after all, left Libya in August.

But the question - both for the State Department, which is conducting an internal investigation, and the House Oversight and Government Reform Committee, which is holding hearings next week - is whether officials in Washington, D.C., specifically at the State Department, were as aware as they should have been about the deteriorating security situation in Libya, and whether officials were doing everything they could to protect Americans in that country.

Earlier this week, the chair of the House Oversight Committee, Rep. Darrell Issa, R-Calif., and another member of the committee wrote to Secretary of State Hillary Clinton listing 13 incidents leading up to the attack, ranging from IED and RPG attacks to a "posting on a pro-Gaddafi Facebook page" publicizing early morning runs taken by the late Ambassador Stevens and his security detail around Tripoli.

"Was State Department headquarters in Washington aware of all the above incidents?" they asked Secretary Clinton, requesting written responses by Oct. 8. "If not, why not? If so, what measures did the State Department take to match the level of security provided to the U.S. Mission in Libya to the level of threat?"