Is it possible to disable ATS in iOS 9 just for debug environment?

Another solution. By using INFOPLIST_PREPROCESS = YES and INFOPLIST_PREPROCESSOR_DEFINITIONS = DEBUG=1,

it can be conditional preprocess like C code using #ifdef or #if directly in Info.plist.

<key>UIMainStoryboardFile</key>
<string>Main</string>
#if DEBUG
<key>NSAppTransportSecurity</key>
<dict>
    <key>NSAllowsArbitraryLoads</key>
    <true/>
</dict>
#endif
<key>UIRequiredDeviceCapabilities</key>
<array>

Cons: Unable to open Xcode's property list editor because it is not well-formed XML :(

My solution is to keep ATS disable option at the default NO value and add a New Run Script Phase to change it in the app bundle's Info.plist when building the app.

This is the script:

#Disables ATS in debug builds.
INFOPLIST="${TARGET_BUILD_DIR}"/"${INFOPLIST_PATH}"
case "${CONFIGURATION}" in
"Release"|"Adhoc")
/usr/libexec/PlistBuddy -c "Set :NSAppTransportSecurity:NSAllowsArbitraryLoads NO" "${INFOPLIST}"
;;
"Debug")
/usr/libexec/PlistBuddy -c "Set :NSAppTransportSecurity:NSAllowsArbitraryLoads YES" "${INFOPLIST}"
;; 
esac