Jokers response came in Batman's usual manner; slipping from stealth to make a grand entrance. Though in this particular case, he switched off the jet's sound dampeners, just before he hit the bridge, and thus Batman appeared on the scene as a giant black shape that roared over the bridge.
He toggled the weapon system, having long sense contemplated the bridge. His usual ordinance of concussion missiles wouldn't work here. They provided a low strength detonation, a large blast radius but the same amount of power as a strong punch. He switched to his other ordinance. A highly explosive mine with a tiny blast radius. He fired them into the trucks blocking the bridge and continued forward.
He listened to the clicking from inside the jet as the weapons load changed to the gas bombs he'd loaded. It would make the joker gas on the bridge inert, but the people who had already breathed it in would still need the anti-toxin. Luckily, Wayne Enterprises had recently manufactured large quantities of it, and donated it to the police and local hospitals.
The bombs dropped on the bridge, along with a healthy dose of flame retardant foam. That ought to be enough to allow fire and rescue workers to get to the survivors on the bridge. The only obstetrical left was Joker's henchmen, and it was time to deal with them.
He pulled the plane into a vertical climb, then switched it to auto pilot. He keyed the "deploy" control, and the armor along the jet's underbelly slid back. The chair in the cockpit lowered, and the backrest folded down leaving Batman lying back and looking at the bridge. He undid the safety harness and dropped from the plane into the open air, extending his wings to let him glide down toward the center of the bridge.
For the last few feet he pulled the cape in, and dropped on the roof of an abandon car. Joker was a priority, so was Jason. He hated to leave them unattended, but for the time being he wasn't about to let these people die, not to serve his own emotional satisfaction.
He looked over the bridge, at the henchmen who surrounded him, and keyed the mines he fired. With a loud crack, the truck at one end of the bridge was ripped in half with both sides it was more then enough of a distraction to allow Batman to leap onto Jokers goons and leave half of them on the ground in pain before any of them had realized what had happened.
Joker wouldn't let himself not be the center of attention, not for long. Batman just hoped it'd be long enough.