Re mutual recognition of security procedures: The US and EU consider their security standards to be the same, hence the arriving pax from the US are allowed to continue onwards without any further security checks. Indias security however is not recognised to be sufficient, so arriving pax have to go thru security again when they transit. The same counts for arrivals into India. Also since there is potential intermingling of arriving pax all have to go thru security again. Not a big deal really. The transit security, although seemingly chaotic, is rather fast in DEL. If you have an AI flight to catch you can ask for an escort to take you to the front of the line. They have about 4-5 people standing behind the transfer desk who do nothing else.