So far no one knows why the needles were placed in the Delta food. Was it a hoax? A prank? An act of sabotage by a disgruntled Gate Gourmet employee? Or a dry run to test airline security?
How Real is the Threat?
Though airlines and the Transportation Safety Administration must treat each threat as serious, an organized terrorist threat is among the least likely explanations. For one thing, the needles were easily detected; out of the six turkey sandwiches that apparently had needles in them, five were discovered before causing injury, and the sixth poked a tiny hole in the passenger's mouth that didn't require medical attention - unnerving though it may be.
Furthermore, putting a pathogen such as HIV on one or more of the needles (especially solid needles, as these are reported to be) is very unlikely to succeed. This is because HIV cannot exist intact for long outside the body; in fact it is rendered inert shortly after contact with air. Thus even if someone got ahold of a quantity of AIDS-infected blood (or even the HIV) and put it on needles (or anything else that might get into another person's bloodstream) to put in airline food, the virus would likely be dead long before the plane took off. Furthermore the flight attendants heated up the sandwiches in ovens before serving them, thus greatly increasing the chance of killing harmful bacteria and viruses.