Error when trying to run app [Android]

Okay so im trying to make an app which has 4 images on the front page. When i click each image i want another window to pop up which in my case doesn't work at all the app craches in some how :/

05-14 17:39:37.714 1886-1886/com.example.flygplanappen.peterjapp I/art﹕ Not late-enabling -Xcheck:jni (already on) 05-14 17:39:42.551 1886-1886/com.example.flygplanappen.peterjapp D/AndroidRuntime﹕ Shutting down VM --------- beginning of crash 05-14 17:39:42.551 1886-1886/com.example.flygplanappen.peterjapp E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: com.example.flygplanappen.peterjapp, PID: 1886 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.flygplanappen.peterjapp/com.example.flygplanappen.peterjapp.flygos}: java.lang.ClassCastException: android.widget.ImageView cannot be cast to android.widget.Button at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360) at android.app.ActivityThread.access$800(ActivityThread.java:144) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5221) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) Caused by: java.lang.ClassCastException: android.widget.ImageView cannot be cast to android.widget.Button at com.example.flygplanappen.peterjapp.flygos.onCreate(flygos.java:19) at android.app.Activity.performCreate(Activity.java:5937) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360) at android.app.ActivityThread.access$800(ActivityThread.java:144) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5221) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) 05-14 17:39:47.695 1982-1982/com.example.flygplanappen.peterjapp D/AndroidRuntime﹕ Shutting down VM 05-14 17:39:47.695 1982-1982/com.example.flygplanappen.peterjapp E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: com.example.flygplanappen.peterjapp, PID: 1982 java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.flygplanappen.peterjapp/com.example.flygplanappen.peterjapp.flygos}: java.lang.ClassCastException: android.widget.ImageView cannot be cast to android.widget.Button at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360) at android.app.ActivityThread.access$800(ActivityThread.java:144) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5221) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) Caused by: java.lang.ClassCastException: android.widget.ImageView cannot be cast to android.widget.Button at com.example.flygplanappen.peterjapp.flygos.onCreate(flygos.java:19) at android.app.Activity.performCreate(Activity.java:5937) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360) at android.app.ActivityThread.access$800(ActivityThread.java:144) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5221) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)