diff --git a/classes.py b/classes.py
index ad036f4..324a63d 100644
--- a/classes.py
+++ b/classes.py
@@ -1,14 +1,24 @@
+"""
+All types used in the project
+"""
+
 from enum import Enum
 import math
 
 
 class ParsingMode(Enum):
+    """
+    Used for parsing
+    """
     LOCATIONS = 1
     FLIGHTSCHEDULE = 2
     FINDCONNECTION = 3
 
 
 class LocationType(Enum):
+    """
+    Differenciate between types of location
+    """
     LOCATION = 1
     HALTESTELLE = 2
     FLUGHAFEN = 3
@@ -27,6 +37,10 @@ class TransportData():
 
 
 class TransportMethod(Enum):
+    """
+    More precise methods of transportation.
+    They are subgroups of TransportKind.
+    """
     WALK = TransportData(0, 4)
     CITY = TransportData(0.189, 30)
     AUTOBAHN = TransportData(0.189, 100)
@@ -37,7 +51,8 @@ class TransportMethod(Enum):
 
 class TransportKind(Enum):
     """
-    distance_penalty
+    General transportation kind.
+    Value: distance_penalty
     """
     INDIVIDUAL = 0.2
     TRAIN = 0.1
@@ -57,14 +72,20 @@ class Coordinate:
 
 
 class Location:
-    def __init__(self, coord: Coordinate, continent: int, name: str, type: LocationType):
+    def __init__(
+            self,
+            coord: Coordinate,
+            continent: int,
+            name: str,
+            type: LocationType):
         self.coord = coord
         self.continent = continent
         self.name = name
         self.type = type
 
     def __str__(self):
-        return f"{{Location: {self.coord}, continent: {self.continent}, name: {self.name}, type: {self.type}}}"
+        return f"{{Location: {self.coord}, continent: {self.continent}, \
+                   name: {self.name}, type: {self.type}}}"
 
     def __repr__(self):
         return self.__str__()
@@ -88,13 +109,18 @@ class Location:
 
 
 class DataSet:
+    """
+    Represent the parsed data
+    """
+
     def __init__(self, locations: dict, flights: dict, connection: tuple):
         self.locations = locations
         self.flights = flights
         self.connection = connection
 
     def __str__(self):
-        return f"locations: {self.locations}, flights: {self.flights}, connection: {self.connection}"
+        return f"locations: {self.locations}, flights: {self.flights}, \
+                 connection: {self.connection}"
 
     def __repr__(self):
         return self.__str__()
diff --git a/dijsktra.py b/dijsktra.py
index 19f9961..dd2c010 100644
--- a/dijsktra.py
+++ b/dijsktra.py
@@ -12,7 +12,9 @@ class Dijkstra():
         self.graph = graph
         self.table = {}
         for vertex in graph:
-            self.table.update({vertex: {"distance": (9999999, 999999), "prev": None}})
+            self.table.update({vertex: {
+                                 "distance": (9999999, 999999),
+                                 "prev": None}})
         self.table[connection[0]]["distance"] = (0, 0)
 
     def algorithm(self, switch: str):
@@ -21,6 +23,7 @@ class Dijkstra():
         print("Performing Dijkstra on the following graph...")
         for vertex in self.graph:
             print(f"{vertex}: {self.graph[vertex]}")
+            print("")
 
         for v1 in self.graph.keys():
             neighbors = self.graph[v1]
@@ -41,7 +44,7 @@ class Dijkstra():
                         self.table[key]["distance"] = (time, co2)
                         self.table[key]["prev"] = v1
 
-        print("self.table:", self.table)
+        print("Final Dijkstra table:", self.table)
 
     def print_result(self, connection: tuple):
         sequence = []
diff --git a/graph.py b/graph.py
index d68a68e..2577574 100644
--- a/graph.py
+++ b/graph.py
@@ -41,19 +41,23 @@ def calc_time(
                 return distance / TransportMethod.WALK.value.speed
             elif distance <= 10 + 1:
                 speed = 1 / TransportMethod.WALK.value.speed
-                return speed + ((distance - 1) / TransportMethod.CITY.value.speed)
+                new_dist = (distance - 1)
+                speed += (new_dist / TransportMethod.CITY.value.speed)
+                return speed
             elif distance < 2000 + 10 + 1:
                 speed = 1 / TransportMethod.WALK.value.speed
                 speed += 10 / TransportMethod.CITY.value.speed
-                return speed + ((distance - 1 - 10) / TransportMethod.AUTOBAHN.value.speed)
+                new_dist = (distance - 1 - 10)
+                speed += (new_dist / TransportMethod.AUTOBAHN.value.speed)
+                return speed
         case TransportKind.TRAIN:
             if distance <= 25:
                 return distance / TransportMethod.OEPNV.value.speed
             else:
                 return (distance / TransportMethod.ICE.value.speed)
         case TransportKind.FLYING:
-            assert(flights != None)
-            assert(frm != None)
+            assert(flights)
+            assert(frm)
             stops = flights[frm]["stops"]
             domestic = flights[frm]["domestic"]
             if domestic:
@@ -100,9 +104,10 @@ def create_graph(dataset: DataSet) -> dict:
 
             # Train
             is_haltestelle = locations[start].type == LocationType.HALTESTELLE
+            is_airport = locations[start].type == LocationType.FLUGHAFEN
             is_same_continent = locations[start].is_same_continent(locations[dest])
             # trains only drive from haltestelle and same continent
-            if is_haltestelle and is_same_continent:
+            if (is_haltestelle or is_airport) and is_same_continent:
                 dest_type = locations[dest].type
                 # there are only trains between haltestellen or airports
                 is_dest_haltestelle = dest_type == LocationType.HALTESTELLE
diff --git a/parser.py b/parser.py
index 8162bbd..b75c72c 100644
--- a/parser.py
+++ b/parser.py
@@ -72,7 +72,10 @@ def parse(filename: str) -> DataSet:
                         domestic = True
                     else:
                         domestic = False
-                    flights.update({id1: {"to": id2, "stops": stops, "domestic": domestic}})
+                    flights.update({id1: {
+                                        "to": id2,
+                                        "stops": stops,
+                                        "domestic": domestic}})
                     continue
                 case ParsingMode.FINDCONNECTION:
                     print("Parsing connection...")