United and JetBlue are expanding their Blue Sky agreement with more benefits for frequent flyers and elites across both airlines. First there was codeshares and the ability to earn miles on select flights of each airline. Next up, there was the ability to redeem miles for award flights on each airlines. Now come the elite like benefits across both airlines. The most anticipated elements of the Blue Sky collaboration between JetBlue and United Airlines begin this week. Now eligible TrueBlue and MileagePlus members can enjoy reciprocal loyalty perks and benefits when traveling across either airlines’ networks.…