same way as your warlock and wizard can stab with their daggers when they must use melee combat.
I don't think that this happens very often in 4th edition at all. In Thunderwave you've got an at will close spell(close spells don't provoke Opportunity Attacks). Unless you're in a situation where you've got a monster in melee range and there's no way you can shift a square so that you won't catch an ally in the burst 3 aoe, there's no reason to use melee at all as a wizard.
In an optimal party, somebody should have a way to bring down flyers. Putting a flyer in prone status will make it fall. A flying creature also has to move at least 2 squares to maintain flight(unless it has the hover property). That means any stun or immobilization effect will also make them fall. Once it's down, a fighter should be able to keep it down for a while with any luck. Here's the powers I found that can bring down a flyer:
Command(Cleric 3)
Enthrall(Cleric 17)
Sacred Word(Cleric 25)
Knockdown Shot(Ranger 13)
Pinning Strike(Ranger 13)
Confounding Arrows(Ranger 15)
Great Ram Arrow(Ranger 19)
Walking Wounded(Rogue 5)
Steel Entrapment(Rogue 23)
Immobilizing Strike(Rogue 23)
Perfect Strike(Rogue 27)
Dread Star(Warlock 1)
Infernal Moon Curse(Warlock 7)
Iron Spike of Dis(Warlock 9)
Tendrils of Thuban(Warlock 15)
Thorns of Venom(Warlock 23)
Tartarean Tomb(Warlock 25)
Thirteen Baleful Stars(Warlock 25)
Hurl Through Hell(Warlock 29)
Icy Terrain(Wizard 1)
Icy Rays(Wizard 3)
Web(Wizard 5)
Spectral Ram(Wizard 7)
Ice Storm(Wizard 9)
Mesmeric Hold(Wizard 13)
Blast of Cold(Wizard 15)
Crushing Titan's Fist(Wizard 17)
Ice Tomb(Wizard 17)
Evard's Black Tentacles(Wizard 19)
Thunderclap(Wizard 23)
Necrotic Web(Wizard 25)
Elemental Maw(Wizard 25)
Prismatic Spray(Wizard 25)
Forcecage(Wizard 27)
Greater Ice Storm(Wizard 29)
Legion's Hold(Wizard 29)
The above list is just ranged stuns, prones, and immobilizes. There's also enemy teleports, and probably other ways of pulling this off.
It's probably worth multiclassing to pick a power like one of the above up if you are melee, especially if you're a fighter. Melee rogues and rangers would be wise to dip into their ranged powers just enough to get a power or two to bring down flyers. I haven't specifically checked, but I suspect there is at least one power for every attribute other than strength up there. Just multiclass based off of your secondary attribute and grab a prone/immob/stun or two.
Or wait for Martial Power, where I'd expect we'll see some powers for heavy thrown that'll do the job.