diff --git a/dotfiles/lib/python/planes.py b/dotfiles/lib/python/planes.py
new file mode 100644
index 00000000..1fc7c9af
--- /dev/null
+++ b/dotfiles/lib/python/planes.py
@@ -0,0 +1,175 @@
+import itertools
+
+from fractions import Fraction
+
+
+class PlaneGroup(object):
+
+    FUEL_CAPACITY = Fraction(1, 1)
+
+    def __init__(
+            self, quantity=1, fuel=None, position=Fraction(0, 1),
+            returning=False
+    ):
+        self.quantity = quantity
+        self.fuel = fuel or quantity * Fraction(1, 1)
+        self.position = position
+        self.returning = returning
+
+    def split(self, quantity=1, fuel=Fraction(0, 0)):
+        new = type(self)(quantity, fuel, self.position, self.returning)
+        remaining = type(self)(
+            quantity=self.quantity - quantity, fuel=self.fuel - fuel,
+            position=self.position, returning=self.returning
+        )
+        return new, remaining
+
+    def split_to_next_max(self):
+        desired_remaining_fuel = (self.quantity - 1) * self.FUEL_CAPACITY
+        turnback_fuel = self.fuel - desired_remaining_fuel
+        return self.split(fuel=turnback_fuel)
+
+    def join(self, other):
+        assert self.position == other.position
+        return type(self)(
+            quantity=self.quantity + other.quantity, fuel=self.fuel + other.fuel,
+            position=self.position, returning=other.returning,
+        )
+
+    @property
+    def effective_position(self):
+        if self.returning:
+            return self.position * -1
+
+    @property
+    def effective_fuel(self):
+        if self.returning:
+            return (self.position + self.FUEL_CAPACITY) * self.quantity
+
+    def distance_to_next_turnback(self, support=None):
+        desired_remaining_fuel = (self.quantity - 1) * self.FUEL_CAPACITY
+        if self.fuel < desired_remaining_fuel:
+            return Fraction(0, 1)
+
+        if support is None:
+            return (
+                (self.fuel - self.position - desired_remaining_fuel)
+                /
+                (self.quantity + 1)
+            )
+
+        fuel_needed_for_turnback = (self.position - support.effective_position)/2
+        target_fuel_at_turnback = (
+            desired_remaining_fuel + fuel_needed_for_turnback
+        )
+        turnback_to_get_to_support = (self.fuel - target_fuel_at_turnback) / self.quantity
+        return turnback_to_get_to_support
+
+    def _advance_to_refuel(self, exact=True):
+        fuel_needed = self._fuel_needed_for_distance(self.position)
+        if exact and fuel_needed != self.fuel:
+            raise Exception("Inexact refuel")
+        return type(self)(
+            quantity=self.quantity, fuel=self.quantity*self.FUEL_CAPACITY
+        )
+
+    def _fuel_needed_for_distance(self, distance):
+        fuel_needed = distance * self.quantity
+        if self.fuel >= fuel_needed:
+            return self.fuel - fuel_needed
+        raise Exception("Not enough fuel")
+
+    def advance(self, distance):
+        if self.returning:
+            if distance < self.position:
+                new_fuel = self.fuel - self._fuel_needed_for_distance(distance)
+                new_position = self.position - distance
+                return type(self)(
+                    fuel=new_fuel, position=new_position, returning=True,
+                    quantity=self.quantity,
+                )
+            else:
+                return self._advance_to_refuel().advance(distance-self.position)
+
+        new_fuel = self.fuel - self._fuel_needed_for_distance(distance)
+        new_position = self.position + distance
+        return type(self)(
+            fuel=new_fuel, position=new_position, quantity=self.quantity,
+        )
+
+
+def run_simulation(plane_count):
+    return SimulationState(PlaneGroup(quantity=plane_count), []).simulate()
+
+
+class SimulationState(object):
+
+    def __init__(self, destination_group, support_groups):
+        self.destination_group = destination_group
+        self.support_groups = support_groups
+
+    @property
+    def supports_by_advancement(self):
+        return sorted(
+            self.support_groups, key=lambda group: group.effective_position,
+            reverse=True,
+        )
+
+    @property
+    def returning_supports(self):
+        return (support for support in self.support_groups if support.returning)
+
+    @property
+    def nearest_support(self):
+        s = self.supports_by_advancement
+        if s:
+            return s[0]
+
+    @property
+    def min_time_to_support_collision(self):
+        min_time_to_collision = float('inf')
+        for returning in self.returning_supports:
+            for support in self.support_groups:
+                distance_between_supports = returning.position - support.effective_position
+                time_to_collision = distance_between_supports/2
+                meeting_position = time_to_collision + support.effective_position
+                if meeting_position > 0:
+                    if time_to_collision < min_time_to_collision:
+                        min_time_to_collision = time_to_collision
+        return min_time_to_collision
+
+    @property
+    def min_turnback_time(self):
+        min_time_to_turnback = float('inf')
+        turnback_group = self.destination_group
+        for support in self.supports_by_advancement:
+            time_to_turnback = turnback_group.distance_to_next_turnback(support)
+            if min_time_to_turnback > time_to_turnback:
+                min_time_to_turnback = time_to_turnback
+            turnback_group = support
+
+        # Check the last group
+        time_to_turnback = turnback_group.distance_to_next_turnback(None)
+        if min_time_to_turnback > time_to_turnback:
+            min_time_to_turnback = time_to_turnback
+        return min_time_to_turnback
+
+    def _advance(self, distance):
+        return type(self)(
+            self.destination_group.advance(distance),
+            [support.advance(distance) for support in self.support_groups],
+        )
+
+    def simulate(self):
+        support_returns = [
+            support.position
+            for support in self.support_groups if support.returning
+        ]
+        next_event = min(
+            support_returns + [self.min_time_to_support_collision, self.min_turnback_time]
+        )
+        self._advance(next_event)
+        nearest_support_return = min(support_returns)
+        return self._advance(nearest_support_return).simulate()
+
+        return self._advance(turnback_distance)._start_turnback()