LONDON — Western intelligence sources said Al Qaida-aligned cells have procured the SA-18 anti-aircraft missile from the former Soviet Union. The sources said the missiles were smuggled into Turkey and acquired by Al Qaida-aligned cells in the Middle East."These are serious missiles and represents a step up in Al Qaida capability," an intelligence source said. On Oct. 28, the French daily Le Figaro reported that Al Qaida-aligned cells have obtained SA-18s for attacks against French airliners. The daily said the cells acquired the missiles in 2002 from the so-called Chechen mafia.