On my, I think London, Paris and Tokyo would be cities that could suffer attacks.
Possibly also Frankfurt and Hong Kong as major financial centres.
Charles de Gaulle Airport, Tokyo Tower, Big Ben, London's and Tokyo's subways.
Assuming a similar mode of attack, CdG, the London Underground, and Tokyo's Metro aren't appropriate targets. Interesting things become possible if you allow bombings, though.
In London, One Canada Square (the "Canary Wharf tower") and the Palace of Westminster are obvious targets. Also Buckingham Palace, which is easier than Parliament to find from the air, but really just a prestige target.
Paris doesn't have an obvious target other than the Eiffel Tower; that's like crashing a plane into the Fantasy Castle at Disney World - spectacular, but pointless. Something in La Defense is probable, but wouldn't have the worldwide impact of the others.
Hamburg has no shortage of targets, but the obvious ones are probably the Deutsche Bank Twin Towers or the Commerzbank Tower. The European Central Bank would be a good bombing target (as would the Bank of England) but is hard to identify and approach from the air.
In Hong Kong, the Bank of China tower is identifiable and accessible. The infamous Kai Tak approach indicates the challenging environment around Hong Kong, though - you might have to settle for 'something in the CBD'. I don't know Tokyo well enough to suggest targets.
If an operation on that large a scale is accepted, I think it's likely that the full list of eleven US targets are gone for... possibly together with the airline bombing element of the Bojinka plot, which originated the 11 September attacks.
Synchronicity would be an issue. If you go for 0800-1000 attacks in the Eastern US, that means 1300-1500 in London, 1400-1600 for mainland Europe, and around midnight for Tokyo and Hong Kong. Possibly also too early for any western US targets. Really, all the attacks need to be done in daylight, and preferably within working hours. That limits you in which cities can be attacked simultaneously - and if the delay between attacks is too long, effective defence becomes possible. Less than two hours between first and last attack in OTL was enough for improvised but effective resistance to arise.