News of the document recently came to light after German newspaper Die Zeit published a story detailing its contents.
The outlet reports that the U.S. Department of Justice gave the letter to the German Federal Office of Justice in April 2012 for the trial of alleged terrorists in Germany, according to a Huffington Post translation of the story.
Johannes Pausch, the lawyer for one of the accused, told the paper he's skeptical about the authenticity of the document.
Written in 2010 by Younis al-Mauritani, a senior al Qaeda operative, the 17-page letter proposes attacks against a variety of targets, including tunnels, bridges, and underwater gas pipelines, the Telegraph notes.
The pipeline idea is explored in some depth, with the operative noting "that the pipelines have safety valves every 6 miles that need to be taken into account when planting mines," according to the news outlet.
Al-Mauritani, who was arrested in Pakistan in 2011, also named a handful of specific targets, including the RAND Corporation research institute in California and the Love Parade, a now-cancelled dance music festival in Germany.
A RAND spokesman told CNN that "as a matter of policy, the RAND Corporation does not comment on specific security issues or potential threats."
The news outlet, who said it received the information from "sources briefed on its contents," reported that al-Mauritani felt operatives should continue to train as pilots and recruits should work for airlines. On the day of the attack, the terrorists could simply drug their co-pilots and fly the plane into the target, CNN reported.
The letter also includes details about al Qaeda's finances and asked for the organization's various regional cells to work together more.
Al-Mauritani was allegedly responsible for al Qaeda international operations, according to the Associated Press, and was supposed to plan direct attacks of "economic importance in America, Europe and Australia."
A document allegedly containing details of al Qaeda's strategy was discovered in north Africa, according to the AP. The document was discovered by members of the press in buildings once used by rebels in Mali.
The letter, which is incomplete, includes a warning to operatives not to be too hasty in implementing strict Shariah law.