[1] It is simply a concentration of flash powder, in a paper case, that is ejected into the air with a black-powder lifting charge, ignited by a fuse.
Single-tube airbombs were banned in Britain in 2004, because they are classed as a cheap nuisance firework.
The airbomb effect, a loud bang and flash, is still part of many larger fireworks.
Since 1 April 2008, any firework having at least one tube containing over 5% flash powder has been classed under United Nations regulations as 1.3G, with stricter transportation and storage regulation.
As such, manufacturers have replaced the "bang" with a crackle effect, or switched to using black-powder bursts.