Failed to start an Appium session

I am seeing this issue frequently, can some one help me out on this. Simulator launch fails with error.
Appium version: Version 1.3.5 (Ophiuchus)
Xcode version: Version 6.1.1 (6A2008a)

Simulator version which I have choosen in exist in the devices list, But still it showiing as Could not find a device to launch.

Log:

info: [debug] Responding to client with error: {“status”:33,“value”:{“message”:“A new session could not be created. (Original error: Could not find a device to launch. You requested ‘iPhone 6 (909326A6-A5ED-4E8A-BAE2-883C313641AB) (8.1 Simulator)’, but the available devices were: [“iPad 2 (8.1 Simulator) [4D058CFB-7C32-442E-B2B4-E42847255B25]”,“iPad Air (8.1 Simulator) [80B49624-5F14-484B-95BF-CB1BFE09749C]”,“iPad Retina (8.1 Simulator) [0478FB5A-768D-420D-A5FA-1B028537B5D5]”,“iPhone 4s (8.1 Simulator) [E9C5E74F-1CEF-4389-9184-4A9A097D4414]”,“iPhone 5 (8.1 Simulator) [50D4F7C7-36B1-4245-90B5-C2E8A99ABC6E]”,“iPhone 5s (8.1 Simulator) [0D6DC205-C7B1-4183-9E9A-F920474BB6A8]”,“iPhone 6 (8.1 Simulator) [909326A6-A5ED-4E8A-BAE2-883C313641AB]”,“iPhone 6 Plus (8.1 Simulator) [49F880FD-3DD8-42E1-884E-0B8059EC8860]”])”,“origValue”:“Could not find a device to launch. You requested ‘iPhone 6 (909326A6-A5ED-4E8A-BAE2-883C313641AB) (8.1 Simulator)’, but the available devices were: [“iPad 2 (8.1 Simulator) [4D058CFB-7C32-442E-B2B4-E42847255B25]”,“iPad Air (8.1 Simulator) [80B49624-5F14-484B-95BF-CB1BFE09749C]”,“iPad Retina (8.1 Simulator) [0478FB5A-768D-420D-A5FA-1B028537B5D5]”,“iPhone 4s (8.1 Simulator) [E9C5E74F-1CEF-4389-9184-4A9A097D4414]”,“iPhone 5 (8.1 Simulator) [50D4F7C7-36B1-4245-90B5-C2E8A99ABC6E]”,“iPhone 5s (8.1 Simulator) [0D6DC205-C7B1-4183-9E9A-F920474BB6A8]”,“iPhone 6 (8.1 Simulator) [909326A6-A5ED-4E8A-BAE2-883C313641AB]”,“iPhone 6 Plus (8.1 Simulator) [49F880FD-3DD8-42E1-884E-0B8059EC8860]”]”},“sessionId”:null}

error: Failed to start an Appium session, err was: Error: Could not find a device to launch. You requested ‘iPhone 6 (909326A6-A5ED-4E8A-BAE2-883C313641AB) (8.1 Simulator)’, but the available devices were: [“iPad 2 (8.1 Simulator) [4D058CFB-7C32-442E-B2B4-E42847255B25]”,“iPad Air (8.1 Simulator) [80B49624-5F14-484B-95BF-CB1BFE09749C]”,“iPad Retina (8.1 Simulator) [0478FB5A-768D-420D-A5FA-1B028537B5D5]”,“iPhone 4s (8.1 Simulator) [E9C5E74F-1CEF-4389-9184-4A9A097D4414]”,“iPhone 5 (8.1 Simulator) [50D4F7C7-36B1-4245-90B5-C2E8A99ABC6E]”,“iPhone 5s (8.1 Simulator) [0D6DC205-C7B1-4183-9E9A-F920474BB6A8]”,“iPhone 6 (8.1 Simulator) [909326A6-A5ED-4E8A-BAE2-883C313641AB]”,“iPhone 6 Plus (8.1 Simulator) [49F880FD-3DD8-42E1-884E-0B8059EC8860]”]

info: <-- POST /wd/hub/session 500 800.055 ms - 1524