I asked this question before but I have a new theory. The ones affected by the time shifting are those who were alive on the island or near it when it flashed away except the Others. But if your'e on the air near the island when it happened, it doesn't have an immediate effect. Sun-Hwa didn't travel back in time because when she got pregnant she took some drugs from the island making her immune to time flashes like the Others. What of Frank? Shouldn't he have gotten a time travel ticket too? Maybe his drunkenness at the time prevented that. What of Juliet Burke? Maybe she's not officially an Other because she's drug free. And what does Jack the Janitor feel about Juliet living with Mr. LeFleur?