The People for the Ethical Treatment of Animals (PETA) India has been campaigning against the airline since it lifted its ban, PETA said in a release.
"Air India's repeated assurances that it will refuse to transport animals to laboratories apparently meant nothing - the airline has gone right back to shipping animals to their deaths", said PETA's Kirsty Henderson.
The protest marks PETA'S first action against Air India in the UK.
According to PETA, "many of the largest and most well-known carriers in their world, including Cathay Pacific, EVA Air, FedEx, Frontier Airlines, Hawaiian Airlines, JetBlue, Korean Air, UPS, US Airways and Virgin Airlines prohibit shipping animals to laboratories.
Jet Airways, India's second-largest airline, also recently committed to a ban on transporting animals slated for experimentation.