Abdulmutallab had appealed his sentence, arguing a lower federal court had erred by accepting his guilty plea despite doubts about his competency, allowing him to represent himself at trial and admitting incriminating statements he made to authorities before being read his rights. He also said his life sentence is cruel and unusual punishment.
But the 6th U.S. Circuit Court of Appeals decided "none of these claims have merit" and affirmed the U.S. District Court's handling of his case.
Abdulmutallab attempted to detonate an explosive device in his underwear on Christmas Day 2009, a few months after he had traveled to Yemen to join up with a violent jihadist group associated with al-Qaida.
In ruling the District Court did not err in ordering a competency hearing, the appellate judges said Abdulmutallab took a "deliberate, conscious and complicated path ... to pursue in the name of martyrdom."
The court said he "not only acted rationally, but was (nearly) able to execute a complex martyrdom mission."
"The complexity behind Abdulmutallab's mission indicates the exact opposite of incompetence," the court said.
The appellate judges also noted he had considerable legal assistance in his defense.
"Standby counsel actually undertook a majority of the representation, as evidenced by the fact that he wrote and filed most motions, examined all witnesses at the suppression hearing, and questioned all but one of the prospective jurors," the court said. "Thus, while Abdulmutallab proceeded pro se, he was represented by legal counsel throughout the proceedings."