Aviation action, computer sleuthing, Islamic politics--uneasily mixed, by prolific suspense-man Williams, in an initially involving but very slow-paced thriller about a six-plane mission with a super-mysterious purpose and destination. Ex-RAF pilot Charles Rawcliffe, bored with his failing liquor store, picks up the challenge when a young pilot-chum tells him about turning down a high-paying mystery mission. And while Rawcliffe is being roughed up, then taken on by the slimies who are running this mission (they kill Rawcliff's pilotchum for his loose tongue), British Intelligence types are wondering about a rumored Mideast-related operation (supposedly a Red Cross mercy mission) backed by a French gangster: planes are being bought, pilots hired, plus elaborate hi-fi equipment! What's the mission? No one knows--but now the six mercenary pilots and nurse Jo are shipped to Cyprus, where they prepare to take off (first a dry run, then the real one) in ""six clapped-out Hercules"" on a tiny runway without lights, radar, or radio (navigation by computer). Other problems, too: an attack by a Cypriot splinter group; inter-pilot fights; indications that some of the pilots (and Jo) are undercover agents for the U.S., U.K., or Israel. So Rawcliff, sure that this mission is an evil one, tries to learn the destination--by having wife Judith back home (a computer analyst) sleuth around London for the computer-programs designed to navigate the mission. And, while the dry run goes ahead (involving a forced stop in Jedda and one death), Judith does learn the apparent target: a Soviet plutonium plant in Yemen. But when the mission finally happens--the pilots get on course, then bail out as each plane goes on to become a ""giant napalm-cum-anti-personnel bomb""--it turns out that it's a Soviet anti-Islamic Revival attack on Mecca at the height of the Hadj. That revelation is hardly worth the nearly 400 pages of buildup--but patient readers will find some gritty aeronautics along the way, together with dullish Mideast lectures, serviceable characterization (sadists and cynics among the pilots), and much leisurely chatter.