No one on board the aircraft flying from Denver to Honolulu suffered any injuries but dramatic videos showed engine parts of the jetliner falling off after one of the engines caught fire.
As many as 40 million people have been vaccinated in the United States and 16 million in the UK. Closer home in Asia, India has vaccinated more than 10 million people so far.
Singapore has been on high alert for several years now, after the rise of Isis in the Middle East attracted recruits from a host of Southeast Asian countries.