We are witnessing a change taking place in the English language where the indefinite pronouns each, any, anyone, everyone and everybody that were once always considered singular are now becoming plurals. This is happening because English does not have a gender non-specific personal pronoun to go with the indefinite pronoun when it functions as an antecedent.
Look at these examples:
Everyone should have his book.
This is the way that I learned to write this sentence. Feminists objected to being called "he," so now the fashionable way to say this to a mixed-gender audience is:
Everyone should have their book.
So now, each person will drive their (not his) own car. Anyone who wants their (not his) picture taken should be here early.
Even though the example you cited about the cell phones does not have this gender issue, it is nonetheless a victim of this ongoing change from singular to plural indefinite pronouns. If you are writing a paragraph like this, use "most people," "many airline passengers" or something other than "everyone." In language, like many things, avoidance is a good way to deal with controversy.
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